Note: Descriptions are shown in the official language in which they were submitted.
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This disclosure is in the field of materials and construction methods useful
in chemical
energy storage and power devices such as, but not limited to, batteries.
BACKGROUND OF THE INVENTION
Metal oxides are compounds in which oxygen is bonded to metal, having a
general formula
MmOx. They are found in nature but can be artificially synthesized. In
synthetic metal oxides the
method of synthesis can have broad effects on the nature of the surface,
including its acid/base
characteristics. A change in the character of the surface can alter the
properties of the oxide,
affecting such things as its catalytic activity and electron mobility. The
mechanisms by which the
surface controls reactivity, however, are not always well characterized or
understood. In
photocatalysis, for example, the surface hydroxyl groups are thought to
promote electron transfer
from the conduction band to chemisorbed oxygen molecules.
Despite the importance of surface characteristics, the metal oxide literature,
both scientific
papers and patents, is largely devoted to creating new, nanoscale, crystalline
forms of metal oxides
for improved energy storage and power applications. Metal oxide surface
characteristics are
ignored and, outside of the chemical catalysis literature, very little
innovation is directed toward
controlling or altering the surfaces of known metal oxides to achieve
performance goals.
The chemical catalysis literature is largely devoted to the creation of
"superacids" ¨
acidity greater than that of pure sulfuric acid (18.4 M H2SO4)
_____________________ often used for large-scale
reactions such as hydrocarbon cracking. Superacidity cannot be measured on the
traditional pH
scale, and is instead quantified by Hammett numbers. Hammett numbers (Ho) can
be thought of as
extending the pH scale into negative numbers below zero. Pure sulfuric acid
has an Ho of -12.
There are, however, many reaction systems and many applications for which
superacidity
is too strong. Superacidity may, for example, degrade system components or
catalyze unwanted
side reactions. However, acidity may still be useful in these same
applications to provide enhanced
reactivity and rate characteristics or improved electron mobility.
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The battery literature teaches that acidic groups are detrimental in
batteries, where they can
attack metal current collectors and housings and cause deterioration in other
electrode components.
Further, the prior art teaches that an active, catalytic electrode surface
leads to electrolyte
decomposition which can result in gas generation within the cell and
ultimately in cell failure.
A need exists for battery implementation having a synthetic metal oxide that
is acidic but
not superacidic at least on its surface and is deployed within the anode
and/or cathode. Further,
existing battery construction techniques should be updated to take full
advantage of the new
materials available according to the present disclosure, as well as taking
advantage of gains and
improvements that may be realized using such construction techniques with
previously known
materials.
SUMMARY OF THE INVENTION
Embodiments of an ultra-high capacity battery cell have a lithiati on capacity
of at least
4000 mAhr/g and comprise an electrode that includes a layer containing a
nanoparticle-sized metal
oxide in a range of 20% to 40% by weight, and a nanoparticle-sized conductive
carbon in a range
of 20% to 40% by weight. In a particular embodiment, the metal oxide and the
conductive carbon
are each 33% by weight. In further embodiments, the metal oxide and the
conductive carbon are
each 20-25% by weight. In a further particular embodiment, the metal oxide and
the conductive
carbon are each 21% by weight. The electrode may be arranged as an anode or
cathode.
The battery cell may include least one other layer also containing the
nanoparticle-sized
conductive carbon and arranged adjacent to the layer containing the
nanoparticle sized metal oxide.
In some embodiments, this other layer is both above and below the layer
containing the
nanoparticle-sized metal oxide. The nanoparticle-sized metal oxide may be an
acidified metal
oxide having, at least on its surface, a pH < 5 when measured in water at 5%
wgt., and a Hammettt
function > -12 (hereafter, an acidified metal oxide, or "AMO"). In other
embodiments, a metal
oxide may be used in construction of the cell or battery that is not
acidified, not substantially
acidified, or not functionalized with an acidic group (here after a non-
acidified metal oxide, or
"non-AMO"). Collectively, AMO' s and non-AMOs may be referred to simply as
metal oxides.
This disclosure describes materials corresponding to AMOs, non-AMOs, and
applications
for using both. Applications include, without limitation, battery electrode
materials, as catalysts,
as photovoltaic or photoactive components, and sensors. Techniques for
preparing AMOs and
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non-AMOs and devices comprising either are further disclosed. The disclosed
AMOs are
optionally used in combination with acidic species to enhance their utility.
This application further describes high capacity electrochemical cells
including electrodes
comprising AMOs and non-AMOs. Techniques for preparing metal oxides and
electrochemical
cells comprising metal oxides are further disclosed. Optionally, the disclosed
metal oxides are
used in conjunction with conductive materials to form electrodes. The formed
electrodes are useful
with metallic lithium and conventional lithium ion electrodes as the
corresponding counter
electrodes. The disclosed metal oxides are optionally used in combination with
acidic species to
enhance their utility.
In some embodiments, the present disclosure provides for layered electrode
constructions
of low active material (i.e., metal oxide) loading. In some cases, less than
80%, by weight of active
material is utilized in the electrode. This contrasts with conventional
electrochemical cell
technology in which the loading of active material is attempted to be
maximized, and may be
greater than or about 80%, by weight, e.g., 90% or 95% or 99%. While high
active material loading
may be useful for increasing capacity in conventional electrochemical cell
technology, the
inventors of the present application have found that reducing the active
material loading actually
permits higher cell capacities with various embodiments according to the
present disclosure. Such
capacity increase may be achieved, at least in part, by allowing for larger
uptake of shuttle ions
(i.e., lithium ions) since additional physical volume may be available when
the active material
loading levels are lower. Such capacity increase may alternatively or
additionally, at least in part,
be achieved by allowing for more active sites for uptake of shuttle ions and
less blocking of active
sites by additional material mass.
The metal oxides described include those in the form of a nanomaterial, such
as a
nanoparticulate form, which may be monodispersed or substantially
monodispersed and have
particle sizes less than 100 nm, for example. The disclosed AMOs exhibit low
pH, such as less
than 7 (e.g., between 0 and 7), when suspended in water or resuspended in
water after drying, such
as at a particular concentration (e.g., 5 wt. %), and further exhibit a
Hammettt function, HO, that
is greater than -12 (i.e., not superaci di c), at least on the surface of the
AMO.
The surface of the AMOs may optionally be functionalized, such as by acidic
species or
other electron withdrawing species. Synthesis and surface functionalization
may be accomplished
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in a "single-pot" hydrothermal method in which the surface of the metal oxide
is functionalized as
the metal oxide is being synthesized from appropriate precursors. In some
embodiments, this
single-pot method does not require any additional step or steps for
acidification beyond those
required to synthesize the metal oxide itself, and results in an AMO material
having the desired
surface acidity (but not superacidic).
Optionally, surface functionalization occurs using strong electron-withdrawing
groups
("EWGs") ¨ such as SO4, PO4, or halogens (Br, Cl, etc.) ¨ either alone or in
some combination
with one another. Surface functionalization may also occur using EWGs that are
weaker than SO4,
PO4, or halogens. For example, the synthesized metal oxides may be surface-
functionalized with
acetate (CH3C00), oxalate (C204), and citrate (C61+07) groups.
Despite the conventional knowledge that acidic species are undesirable in
batteries because
they can attack metal current collectors and housings and cause deterioration
in other electrode
components, and that active, catalytic electrode surfaces can lead to
electrolyte decomposition, gas
generation within the cell, and ultimately in cell failure, the inventors have
discovered that acidic
species and components can be advantageous in batteries employing AlVIO
materials in battery
electrodes.
For example, the combination or use of metal oxides with acidic species can
enhance the
performance of the resultant materials, systems or devices, yielding improved
capacity, cyclability,
and longevity of devices. As an example, batteries employing acidic
electrolytes or electrolytes
containing acidic species as described herein exhibit considerable gains in
capacity, such as up to
100 mAh/g or more greater than similar batteries employing non-acidified
electrolytes or
electrolytes lacking acidic species. In some embodiments, improvements in
capacity between 50
and 300 mAh/g may be achieved In addition, absolute capacities of up to 1000
mAh/g or more
are achievable using batteries having acidified electrolytes or electrolytes
including acidic species.
Moreover, cycle life of a battery may be improved through the use of acidic
electrolytes or
electrolytes containing acidic species, such as where a battery's cycle life
is extended by up to 100
or more charge-discharge cycles.
An example battery cell comprises a first electrode, such as a first electrode
that comprises
a metal oxide (optionally an AMO nanomaterial), a conductive material, and a
binder; a second
electrode, such as a second electrode that includes metallic lithium, and an
electrolyte positioned
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metal oxide comprises less
than 80 weight percent of the first electrode. Example electrolytes include
those comprising a
metal salt dissolved in a solvent, solid electrolytes, and gel electrolytes.
Optionally, a separator is
positioned between the first electrode and the second electrode.
In addition or alternatively, batteries including an electrode, such as a
cathode or anode,
that is itself acidic or that includes acidic species, such as an organic
acid, may also be beneficial
and, again, contrary to the conventional teaching in battery technology. For
example, batteries
incorporating acidic electrodes or acidic species within the electrode may
enhance the performance
and yield improved capacity, cyclability, and longevity. Capacity gains of up
to 100 mAh/g or
greater are achievable. Cycle life of a battery may also be improved through
the use of acidic
electrodes or electrodes containing acidic species, such as where a battery's
cycle life is extended
by up to 100 or more cycles. As an example, an acidic electrode or an
electrode that includes
acidic species may exhibit a pH less than 7 (but not be superacidic), such as
when components of
the electrode are suspended in water (or resuspended in water after drying) at
5 wt. %.
Electrodes corresponding to the present disclosure may comprises a layered
structure
including a first set of layers comprising a conductive material and a second
set of layers
comprising the metal oxide. Optionally, the first set of layers and the second
set of layers may be
provided in an alternating configuration. Optionally, the first set of layers
and the second set of
layers independently comprises between 1 and 20 layers. Optionally, the first
set of layers and the
second set of layers independently have thicknesses of between 1 im and 50 um,
between 2 um
and 25 um, between 3 um and 20 um, between 4 um and 15 um, or between 5 um and
10 um.
Optionally, the metal oxide comprises between 5 and 90 weight percent of the
second set of layers,
such as 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or
90 weight percent.
Optionally, the conductive material and the binder each independently comprise
between 5 and 90
weight percent of the first set of layers such as 25, 10, 15, 20, 25, 30, 35,
40, 45, 50, 55, 60, 65,
70, 75, 80, 85, or 90 weight percent.
A first electrode optionally comprises the metal oxide at up to 95 weight
percent of the first
electrode, up to 80 weight percent of the first electrode, up to 70 weight
percent of the first
electrode, between 1 and 50 weight percent of the first electrode, between 1
and 33 weight percent
of the first electrode, between 15 and 25 weight percent of the first
electrode, between 55 and 70
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weight percent of the first electrode, between 20 and 35 weight percent of the
first electrode,
between 5 and 15 weight percent of the first electrode. Specific examples of
metal oxide weight
percent for the first electrode include 1%, 5%, 11%, 12%, 13%, 14%, 21%, 22%,
23%, 24%, 25%,
26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 60%, 61%, 62%, 63%, 64%, 65%, etc.
Without
limitation loadings (percent metal oxide) of the electrode may range from 1-
95%, 10-80%, 20-
70%; 30-40%; 40-50%; 50-60%; 60-70%; or 80-100%. In various embodiments, the
loading
values may vary by +/- 1%, 2%, 5%, or 10% Optionally, the conductive material
and the binder
each independently comprise the majority of the remainder of the first
electrode. For example, the
conductive material and the binder each independently comprise between 10 and
74 weight percent
of the first electrode. Optionally, the conductive material and the binder
each together comprise
between 20 and 90 weight percent of the first electrode. Optionally, an AMO
nanomaterial is
added as a dopant of 1-10% by weight to a conventional lithium ion electrode,
such as graphite,
lithium cobalt oxide, etc.
Various materials are useful for the electrodes described herein. Example
metal oxides
include, but are not limited to, a lithium containing oxide, an aluminum
oxide, a titanium oxide, a
manganese oxide, an iron oxide, a zirconium oxide, an indium oxide, a tin
oxide, an antimony
oxide, a bismuth oxide, or any combination of these. Optionally, the oxides
are in the form of an
AMO. As described herein, the metal oxide optionally comprises and/or is
surface functionalized
by one or more electron withdrawing groups selected from Cl, Br, B03, SO4,
PO4, NO3, CH3C00,
C204, C2H204, C6E1807, or C6H507. Example conductive material comprises one or
more of
graphite, conductive carbon, carbon black, Ketjenblack, or conductive
polymers, such as poly(3,4-
ethylenedioxythiophene) (PEDOT), polystyrene sulfonate (PS S), PEDOT:P SS
composite,
polyaniline (PANI), or polypyrrole (PPY).
In some embodiments, electrodes comprising A1\40 nanomaterials are used in
conjunction
with other electrodes to form a cell. For example, a second electrode of such
a cell may comprise
graphite, metallic lithium, sodium metal, lithium cobalt oxide, lithium
titanate, lithium manganese
oxide, lithium nickel manganese cobalt oxide (NMC), lithium iron phosphate,
lithium nickel cobalt
aluminum oxide (NCA), an AMO nanomaterial, or any combination of these. In a
specific
embodiment, the first electrode comprises an SnO2 (in A1\40 or non-AMO form),
and the second
electrode comprises metallic lithium.
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Various materials are useful for the electrodes described herein. Example
metal oxides
include, but are not limited to, a lithium containing oxide, an aluminum
oxide, a titanium oxide, a
manganese oxide, an iron oxide, a zirconium oxide, an indium oxide, a tin
oxide, an antimony
oxide, a bismuth oxide, or any combination of these. Optionally, the oxides
are in the form of an
AIVIO. As described herein, the metal oxide optionally comprises and/or is
surface functionalized
by one or more electron withdrawing groups selected from Cl, Br, B03, SO4,
PO4, NO3, CH3C00,
C204, C2H204, C6I-1807, or C6H507. Example, conductive material comprises one
or more of
graphite, conductive carbon, carbon black, Ketjenblack, or conductive
polymers, such as poly (3,4-
ethylenedioxythiophene) (PEDOT), polystyrene sulfonate (PS S), PEDOT :P SS
composite,
polyaniline (PANI), or polypyrrole (PPY).
In various embodiments, high capacity battery cells comprise a first electrode
including a
metal oxide nanomaterial, a conductive material, and a binder; a second
electrode; and an
electrolyte positioned between the first electrode and the second electrode,
where the metal oxide
nanomaterial comprises 5-15, 20-35, or 55-70 weight percent of the first
electrode, where the metal
oxide nanomaterial comprises 0-15% by weight of iron oxide and 85-100% by
weight of tin oxide.
In some embodiment, metal oxide comprises and/or is surface functionalized by
one or more
electron withdrawing groups, where the conductive material comprises one or
more of graphite,
conductive carbon, carbon black, Ketjenblack, and conductive polymers, such as
poly (3, 4-
ethylenedioxythiophene) (PEDOT), polystyrene sulfonate (PSS), PEDOT :P SS
composite,
polyaniline (PANT), or polypyrrole (PPY), where the second electrode comprises
or includes
metallic lithium.
Such a high capacity battery cell may exhibit a life cycle of 100 to 1000
charge-discharge
cycles without failure, and an open circuit voltage upon assembly of between 2
V and 4 V.
Optionally, the first electrode comprises a layered structure including a
first set of layers the
conductive material and a second set of layers comprising the metal oxide
nanomaterial, such as
where the first set of layers and the second set of layers are provided in an
alternating configuration,
where the first set of layers comprises between 1 and 20 layers and where the
second set of layers
comprises between 1 and 20 layers, where the first set of layers and the
second set of layers
independently have thicknesses of between 1 p.m and 50 p.m, where the metal
oxide nanomaterial
comprises between 5 and 70 weight percent of the second set of layers.
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As a further example, batteries in which the electrode is formed using a
slurry may also be
beneficial and contrary to the conventional teaching in battery technology. As
described herein,
the metal oxide may optionally be formed into battery electrode by first
forming a slurry of the
metal oxide with one or more binder compounds, solvents, additives (e.g.,
conductive additives or
acidic additives), and/or other wet processing materials. The slurry may be
deposited on a
conductive material or current collector in order to form an electrode. Such a
slurry and/or a
solvent may optionally be acidic or include acidic species and, again, allow
for improvements in
capacity, cyclability, and longevity of the resultant battery. Optionally, all
or a portion of the
solvent may be evaporated, leaving the metal oxide material, binder,
additives, etc. The resultant
material (in the case of using an AMO) may optionally exhibit its own acidity,
such having a pH
less than 7 (but not superacidic), when suspended in water (or resuspended in
water after drying)
at 5 wt. %, for example.
Various techniques may be used for making the metal oxide. Optionally, making
a metal
oxide comprises forming a solution comprising a metal salt, ethanol, and
water; acidifying the
solution by adding an acid to the solution, basifying the solution by adding
an aqueous base to the
solution; collecting precipitate from the solution; washing the precipitate;
and drying the
precipitate.
Optionally, making an electrode further comprises depositing a further
conductive layer
over the electrode layer, such as a conductive layer that comprises a second
conductive material.
Optionally, depositing the conductive layer include forming a conductive
slurry using the second
conductive material, a second binder, and a second solvent; depositing a
conductive slurry layer
on the electrode layer; and evaporating at least a portion of the second
solvent to form the
conductive layer. Optionally, making an electrode comprises forming 1-20
additional conductive
layers comprising the conductive material and 1-20 additional electrode layers
comprising the
metal oxide. For example, an electrode may comprise a layered structure
including a first set of
layers comprising a second conductive material and a second set of layers
comprising the metal
oxide, such as where the first set of layers and the second set of layers are
provided in an alternating
configuration. Example layers include those independently having thicknesses
of between 1 pm
and 50 p.m. Example layers include those comprising between 10 and 90 weight
percent of the
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metal oxide. Example layers include those independently comprising between 5
and 85 weight
percent of the conductive material and/or binder.
Electrodes formed using the methods of this aspect may have a metal oxide
content of up
to 80 weight percent. Electrodes formed using the methods of this aspect may
have a conductive
material and/or binder content of between 10 and 70 weight percent of the
electrode.
As described above, acidic species may optionally be included as an additive
to any of the
components of a battery, such as an electrode or an electrolyte. Optionally, a
battery comprising
a metal oxides according to the present disclosure may include an electrolyte
positioned between
the electrodes in which acidic species are dissolved in a solvent. Such an
electrolyte may also be
referred to herein as an acidified electrolyte. The electrolyte may optionally
include one or more
lithium salts dissolved in the solvent, such as LiPF6, LiAsF6, LiC104, LiBF4,
LiCF3S03, and
combinations of these. It will be appreciated that the electrolyte may be
positioned not only in the
space separating the electrodes (i.e., between the electrodes), but may also
penetrate through or
into pores of the electrodes and/or through or into pores of any materials or
structures optionally
positioned between the electrodes, such as a separator.
Example acidic species useful with the AMOs, electrodes, and electrolytes
described herein
include but are not limited to organic acids, such as carboxylic acids.
Example acidic species
include those exhibiting a pKa in water of between -10 and 7, between -5 and
6, between 1 and 6,
between 1.2 and 5.6, or about 4. Specific example organic acids include, for
example, oxalic acid,
carbonic acid, citric acid, maleic acid, methylmalonic acid, formic acid,
glutaric acid, succinic
acid, methylsuccinic acid, methylenesuccinic acid, citraconic acid, acetic
acid, benzoic acid.
0
Example organic acids include dicarboxylic acids, such as those having a
formula of HO
where R is a substituted or unsubstituted C1-C20 hydrocarbon, such as a
substituted or
unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a
substituted or
unsubstituted aromatic or heteroaromatic, a substituted or unsubstituted
amine, etc. Example
0 0
organic acids also include those having a formula of HO OH
where L is a substituted or
unsubstituted C1-C20 divalent hydrocarbon, such as a substituted or
unsubstituted alkylene group,
a substituted or unsubstituted arylene group, a substituted or unsubstituted
heteroarylene group, a
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organic acid anhydrides, such
0 0
as having a formula of where RI- and R2 are independently a
substituted or
unsubstituted C1-C20 hydrocarbon, such as a substituted or unsubstituted alkyl
group, a
substituted or unsubstituted alkenyl group, a substituted or unsubstituted
aromatic or
heteroaromatic group, a substituted or unsubstituted amine, etc. Optionally,
RI and R2 can form a
10 ring. Example organic acid anhydrides include any anhydrides of the
above mentioned organic
acids. Specific organic acid anhydrides include, but are not limited to
glutaric anhydride, succinic
anhydride, methyl succinic anhydride, maleic anhydride, and itaconic
anhydride.
Useful concentrations of the acidic species in either or both the electrolyte
and the AMO
electrode include from 0 wt. % to 10 wt. %, 0.01 wt. % to 10 wt. %, from 0.1
wt. % to 10 wt. %,
from 1 wt. % to 5 wt. %, or from 3 wt. % to 5 wt. %.
Useful solvents include those employed in lithium ion battery systems, for
example, such
as ethylene carbonate, butylene carbonate, propylene carbonate, vinylene
carbonate, dimethyl
carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate,
methylpropyl carbonate,
ethylpropyl carbonate, fluoroethylene carbonate and mixtures thereof. Other
useful solvents will
be appreciated to those skilled in the art. Optionally, when an acidic species
and metal salt are
dissolved in a solvent to form an electrolyte, the electrolyte itself exhibits
an acidic condition (i.e.,
pH less than 7).
Example binders useful with the batteries and electrodes described herein
include Styrene
Butadiene Copolymer (SBR), Polyvinylidene Fluoride (PVDF), Carboxy methyl
cellulose (CMC),
Styrene Butadiene Rubber (SBR), acrylonitrile, polyacrylic acid (PAA),
polyvinyl alcohol (PVA),
polyamide imide (PAT), and any combination of these. Optionally, conductive
polymers may be
useful as a binder.
Other example additives useful with the AMOs and electrodes described herein
include,
but are not limited to conductive additives. Example conductive additives
include graphite,
conductive carbon, carbon black, Ketjenblack, and conductive polymers, such as
poly (3,4-
ethylenedioxythiophene (PEDOT), polystyrene sulfonate (PS S), PEDOT:PSS
composite,
polyaniline (PANT), and polypyrrole (PPY). Conductive additives may be
present, for example,
in an electrode, at any suitable concentration such as at weight percent
greater than 0 and as high
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as 35 wt. %, 40 wt. % or more. Optionally, conductive additives are present in
an electrode at a
range of 1 wt. % to 95 wt. %, 1 wt. % to 35 wt. %, 1 wt. % to 25 wt. %, 5 wt.
% to 40 wt. %, 10
wt. % to 40 wt. %, 15 wt. % to 40 wt. %, 20 wt. % to 40 wt. %, 25 wt. % to 40
wt. %, 30 wt. % to
40 wt. %, 35 wt. % to 40 wt. %, 40 wt. % to 45 wt. %, 40 wt. % to 50 wt. %, 40
wt. % to 55 wt.
%, 40 wt. % to 60 wt. %, 40 wt. % to 65 wt. %, 40 wt. % to 70 wt. %, 40 wt. %
to 75 wt. %, 40
wt. % to 80 wt. %, 40 wt. % to 85 wt. %, 40 wt. % to 90 wt. %, or 40 wt. % to
95 wt. %.
Methods of making batteries are also described herein. An example method of
making a
battery comprises making a metal oxide nanomaterial; forming a first electrode
of or comprising
the nanomaterial; forming an electrolyte by dissolving one or more metal salts
in a solvent; and
positioning the electrolyte between the first electrode and a second
electrode. Another example
method of making a battery comprises making a metal oxide nanomaterial;
forming a first
electrode of or comprising the nanomaterial and one or more metal salts; and
positioning the
electrolyte between the first electrode and a second electrode.
Electrolytes for use in batteries are also disclosed herein. For example, the
disclosed
electrolytes are useful in batteries comprising a first electrode and a second
electrode. Example
electrolytes comprise a solvent and one or more metal salts dissolved in the
solvent. Optionally,
an acidic species is dissolved in the solvent, such as an acidic species that
is different from the one
or more metal salts.
As described above, a variety of acidic species are useful in the disclosed
electrolytes, such
as an acidic species comprising an organic acid and/or an organic acid
anhydride. Example organic
acids include, but are not limited to, oxalic acid, acetic acid, citric acid,
maleic acid, methylmalonic
acid, glutaric acid, succinic acid, methylsuccinic acid, methylenesuccinic
acid, citraconic acid, or
any combination of these. Example organic acid anhydrides include, but are not
limited to glutaric
anhydride, succinic anhydride, methylsuccinic anhydride, maleic anhydride,
itaconic anhydride,
or any combination of these. Other acidic species examples are described
above. Useful acidic
species include, but are not limited to, those exhibiting a pKa of between -10
and 7, between -5
and 6, between 1 and 6, between 1.2 and 5.6, or about 4. The acidic species
may optionally be
present in the electrolyte at any suitable concentration, such as from 0.01
wt. % to 10 wt %, from
0.1 wt. % to 10 wt. %, from 1 wt. % to 5 wt. %, or from 3 wt. % to 5 wt. %.
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It will be appreciated that lithium metal salts, such as LiPF6, LiAsF6,
LiC104, LiBF4,
LiCF3S03, may be useful components of the disclosed acidified electrolytes.
Example solvents
include, but are not limited to, ethylene carbonate, butylene carbonate,
propylene carbonate,
vinylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate,
ethylmethyl
carbonate, methylpropyl carbonate, ethylpropyl carbonate, fluoroethylene
carbonate and mixtures
thereof. Example solvents may be useful in metal ion batteries, such as
lithium ion batteries.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified cutaway view of an example lithium ion battery cell.
FIG. 2 is another simplified cutaway view of a lithium ion battery cell with
the electrolyte
substantially contained by the separator.
FIG. 3 is a schematic of a lithium ion battery comprising multiple cells.
FIG. 4 shows differences in the cyclic voltammogram of AMO tin prepared by the
method
disclosed herein relative to that of commercially available, non-AMO tin when
cycled against Li.
FIG. 5 shows the total reflectance of A1\40 tin oxide is different than that
of commercially
available, non-AMO tin oxide.
FIG. 6 is X-ray photoelectron spectroscopy (XPS) data showing surface
functionalization
arising endogenously from the synthesis method disclosed herein. Numbers shown
are atomic
concentrations in %. The far-right column lists the corresponding pH of the
synthesized
nanoparticles as measured when dispersed at 5 wt% in aqueous solution.
FIG. 7 provides electron micrograph images showing differences in morphology
between
AMO nanoparticles synthesized under identical conditions except for the use of
a different group
for functionalization.
FIG. 8 shows the difference in morphology and performance of AMO nanoparticles
synthesized under identical conditions except for having two different total
reaction times.
FIG. 9 provides representative half-cell data showing differences in behavior
between
spherical and elongated (needle-like or rod-like) AMOs upon cycling against
lithium.
FIG. 10 provides X-ray photoelectron spectroscopy analysis of the surface of
AMO
nanoparticles synthesized using both a strong (phosphorous containing) and
weak (acetate)
electron withdrawing group shows greater atomic concentration of phosphorous
than of the bonds
associated with acetate groups.
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FIG. 11A provides data showing visible light activity degradation data for
different AlVIOs.
FIG. 11B provides data showing ultraviolet light activity degradation data for
different
AMOs.
FIG. 12 is a graph comparing two AMOs, one having higher capacity for use in a
primary
(single use) battery application and the other having higher cyclability for
use in a secondary
(rechargeable) battery application.
FIG. 13 provides charge and discharge capacity data and Columbic efficiency
data,
illustrating that AMOs can result in enhanced battery performance, without
deterioration of battery
components or gas generation.
FIG. 14 shows capacity and cycling data for an AMO in standard, acidified, and
basified
electrolyte systems.
FIG. 15 shows capacity and cycling data for an AMO, and for the same AMO from
which
the acidification was removed by solvent washing.
FIG. 16 is a plot of temperature and voltage for a cell constructed according
to the present
disclosure and subjected to a nail penetration test.
FIG. 17A is a plot of temperature and voltage for a cell constructed according
to the present
disclosure and subjected to an overcharge test.
FIG. 17B is a plot of the overcharge test of FIG. 17A focusing on the start of
the test.
FIG. 18 is a side view of an example cathode according to aspects of the
present disclosure.
FIG. 19 is a bar graph comparing lithiation capacities of various metal oxides
using
standard construction techniques compared to construction techniques according
to the present
disclosure.
FIG. 20 is a graph of voltage versus energy for Mn02 as an active material
blended with
varying amounts of AMO tin oxide according to the present disclosure.
FIG. 21 is a side cutaway view of an alkaline-AMO battery according to aspects
of the
present disclosure.
FIG. 22 is a graph comparing discharge capacity of an alkaline cell comprising
an acidified
SnO2 of this disclosure blended with manganese dioxide and that of a
traditional alkaline electrode.
DEFINITIONS
For the purposes of this disclosure, the following terms have the following
meanings:
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Acidic oxide ¨ a term used generally in the scientific literature to refer to
binary
compounds of oxygen with a nonmetallic element. An example is carbon dioxide,
CO2. The oxides
of some metalloids (e.g., Si, Te, Po) also have weakly acidic properties in
their pure molecular
state.
Acidified metal oxide ("AMO") ¨ a term used here to denote a binary compound
of
oxygen with a metallic element which has been synthesized or modified to have
an acidity greater
than that of its natural mineralogical state and also a Hammett function, Ho >
¨ 12 (not
superacidic). The average particle size is also less than that of the natural
mineralogical state.
Naturally occurring mineralogical forms do not fall within the scope of the
inventive A1\40
material. A synthesized metal oxide, however, that is more acidic than its
most abundant naturally
occurring mineralogical form (of equivalent stoichiometry) but not superacidic
falls within the
bounds of this disclosure and can be said to be an AMO material provided it
satisfies certain other
conditions discussed in this disclosure.
Acidic ¨a term used generally in the scientific literature to refer to
compounds having a
pH of less than 7 in aqueous solution.
Electron-withdrawing group ("EWG") ¨ an atom or molecular group that draws
electron
density towards itself. The strength of the EWG is based upon its known
behavior in chemical
reactions. Halogens, for example are known to be strong EWGs. Organic acid
groups such as
acetate are known to be weakly electron withdrawing.
Hammett function ¨ An additional means of quantifying acidity in highly
concentrated
acid solutions and in superacids, the acidity being defined by the following
equation: Ho = pKBH-
-F log([13]/[BH-F]). On this scale, pure 18.4 molar H2SO4 has a Ho value of -
12. The value Ho = -12
for pure sulfuric acid must not be interpreted as pH = -12, instead it means
that the acid species
present has a protonating ability equivalent to H30+ at a fictitious (ideal)
concentration of 1012
mol/L, as measured by its ability to protonate weak bases. The Hammett acidity
function avoids
water in its equation. It is used herein to provide a quantitative means of
distinguishing the AMO
material from superacids. The Hammett function can be correlated with
colorimetric indicator tests
and temperature programmed desorption results.
Layered construction - As used herein, the term "layered construction" shall
mean a
battery cell comprised of discrete deposits of material (which may or may not
be the same material)
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during construction, but
effectively diminished or eliminated in the final product as specified herein.
Low loading ¨ an active material or mixed layer including an active material
wherein the
active material is present in amounts in a range of 10% wgt. to 80% wgt.
Metal oxide ¨ a term used generally in the scientific literature to refer to
binary compounds
10 of oxygen with a metallic element. Depending on their position in the
periodic table, metal oxides
range from weakly basic to amphoteric (showing both acidic and basic
properties) in their pure
molecular state. Weakly basic metal oxides are the oxides of lithium, sodium,
magnesium,
potassium, calcium, rubidium, strontium, indium, cesium, barium and tellurium.
Amphoteric
oxides are those of beryllium, aluminum, gallium, germanium, astatine, tin,
antimony, lead and
15 bismuth.
Monodisperse ¨ characterized by particles of uniform size which are
substantially
separated from one another, not agglomerated as grains of a larger particle.
pH ¨ a functional numeric scale used generally in the scientific literature to
specify the
acidity or alkalinity of an aqueous solution. It is the negative of the
logarithm of the concentration
of the hydronium ion [H301. As used here it describes the relative acidity of
nanoparticles
suspended in aqueous solution.
Surface functionalization - attachment of small atoms or molecular groups to
the surface
of a material.
Superacid - substances that are more acidic than 100% H2 SO4, having a Hammett
function,
Ho < ¨12.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Described herein are high capacity electrochemical cells and cell components,
such as
electrodes, for such cells. The disclosed electrochemical cells and electrodes
comprise metal
oxides, which may be AMO or non-AMO nanomaterials, and exhibit high capacity.
In
embodiments, the metal oxides are provided at a relatively low loading (weight
percent) in the
electrodes, such as at weight percents less than 30 %, with the majority of
the remainder of the
electrodes comprising conductive materials and binders. Even with such low
loadings, capacities
of greater than 10,000 mAh/g in the case of AMO nanomaterial has been
observed. The electrodes
may be provided in layered or non-layered configurations. Example layered
configurations
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include separate layers including A1\40 nanomaterial and low loading or non-
AMO containing
layers. In other embodiments non-AMO metal oxides may be layered with other
non-AMO metal
oxides of the same of different material. In further embodiment, layers may
include both AMO
and non-AMO metal oxides in the same layered structure. The layering of
electrodes is optional,
however, and high capacities are observed in both layered and non-layered
electrodes.
Referring now to Figure 1, a lithium ion battery cell 100 is illustrated in a
simplified
cutaway view. The cell 100 may comprise a casing or container 102. In some
embodiments, the
casing 102 is a polymer or an alloy. The casing 102 chemically and
electrically isolates the
contents of the cell 100 from adjacent cells, from contamination, and from
damaging or being
damaged by other components of the device into which the cell 100 is
installed. A full battery
may contain a plurality of cells arranged in a series and/or parallel
configuration. The battery may
have a further casing or securement mechanism binding the plurality of cells
together as is known
in the art.
The cell 100 provides a cathode 104 and an anode 106. The contents of the cell
100
undergo a chemical reaction when a conduction path is provided between the
cathode 104 and
anode 106 that is external to the cell 100. As a result of the chemical
reaction, electrons are
provided at the anode 106 that flow to the cathode 104 via the circuit
provided external to the
battery (sometimes referred to as the load). At a basic level, during
discharge of the cell 100, the
materials comprising the anode 106 are oxidized providing the electrons that
flow through the
circuit. The materials comprising the cathode 104, as recipient of the
electrons given up by the
anode 106, are reduced.
Within the cell 100, during discharge, metallic cations move through an
electrolyte 108
from the anode 106 to the cathode 104. In the case of a lithium based battery,
the metallic cation
may be a lithium cation (Li+). The electrolyte 108 may be a liquid electrolyte
such as a lithium
salt in an organic solvent (e.g., LiC104 in ethylene carbonate).
Other lithium based
electrolyte/solvent combinations may be used as are known in the art. In some
cases the electrolyte
108 may be a solid electrolyte such as a lithium salt in a polyethylene oxide.
Optionally, the
electrolyte may comprise a polymer electrolyte. Example electrolytes include
those described in
U.S. Patent Application Publication 2017/0069931, which is hereby incorporated
by reference.
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A separator 110 may be employed to prevent contact between the electrodes 104,
106. The
separator 110 may be a porous layer of material that is permeable to the
lithium ions and the
electrolyte 108 but not otherwise electrically conductive so as to prevent
internal shorting of the
cell 100. As is known in the art, the separator 110 may comprise glass fibers
or may comprise a
polymer, possibly with a semi-crystalline structure. Additional components,
such as current
collectors, may also be included in the cell 100, but are not shown in FIG. 1.
Together the anode 104, cathode 106, electrolyte 108, and separator 110 form
the
completed cell 100. Since the separator 110 is porous, the electrolyte 108 may
flow into, or be
contained by, the separator 110. Under normal operating conditions, the
porosity of the separator
110 allows for ion (Li+) flow between the electrodes 104, 106 via the
electrolyte 108. As is known
in the art, a separator can be constructed so as to melt and close the
internal pore structure to shut
down the cell in the event of exposure to excess heat or a runaway exothermic
reaction.
Most lithium-based cells are so-called secondary batteries. They can be
discharged and
recharged many times before the chemical or structural integrity of the cell
falls below acceptable
limits. Cells and batteries according to the present disclosure are considered
to be both primary
(e.g., single use) and secondary batteries.
In the case of the cell 100 being a secondary cell (or part of a secondary
battery) it should
be understood that the cell 100 may be recharged either alone or as a
component of a completed
system wherein multiple cells are recharged simultaneously (and possibly in
the same parallel or
series circuit).
A reverse voltage is applied to the cell 100 in order to effect charging. It
should be
understood that various schemes for effective recharging of lithium batteries
can be employed.
Constant current, variable current, constant voltage, variable voltage,
partial duty cycles, etc., may
be employed. The present disclosure is not intended to be limited to a
particular charging
methodology unless stated in the claims. During charging of cell 100, element
115 represents a
voltage source that is applied between cathode 104 and anode 106 to provide
electrons from
cathode 105 to anode 106 and allow chemical reactions to take place. Lithium
ions are shuttled
from cathode 104 to the anode 106 through electrolyte 108 and separator 110.
As examples, cathode 104 or anode 106 may independently comprise a metal oxide
according to the present disclosure. The metal oxide may be a nano-material,
possibly
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substantially monodispersed, and in either AMO or non-AMO form. For use of an
AMO material
as a cathode, an anode may correspond to lithium metal or a lithium
intercalation material, such as
graphite. Non-AMO cathodes may also be paired with an anode that may
correspond to lithium
metal or a lithium intercalation material. Optionally, electrolyte 108 may
include an acidic species,
such as dissolved in an organic solvent with a lithium salt. In addition to or
alternative to use of
an acidic species in electrolyte 108, an electrode (i.e., cathode 104 or anode
106) may optionally
comprise an AMO and an acidic species. Oxalic acid is an exemplary acidic
species.
Without wishing to be bound by any theory, it is believed that the presence of
acidic species
in the cathode 104 or anode 106 and/or electrolyte 108 improves a surface
affinity of A1\40
materials toward lithium ions, resulting in an improved ability to take up
lithium ions during
discharge and overall improvement to capacity as compared to a similar cell
lacking acidic species
or having a basified electrode or electrolyte (i.e., including basic species).
Alternatively or
additionally, the presence of acidic species may allow for additional active
sites for lithium uptake
in cathode 104.
It should be understood that Figure 1 is not to scale. A shown in Figure 2, in
most
applications, the separator 110 occupies most or all of the space between the
electrodes 104, 106
and is in contact with the electrodes 104, 106. In such case, the electrolyte
108 is contained within
the separator 110 (but may also intrude into the pores or surface of the anode
or cathode). Figure
2 is also not necessarily to scale. The actual geometry of a cell can range
from relatively thin and
flat pouches, to canister type constructions, to button cells and others. Cell
construction techniques
such as winding or bobbin or pin type assemblies may be used.
Current collectors known in the art and other components (not shown) may also
be relied
upon to form a cell 100 into a commercially viable package. Although overall
shape or geometry
may vary, a cell or battery will normally, at some location or cross section,
contain the electrodes
104, 106 separated rather than touching, and have the electrolyte 108 and
possibly separator 110
between them. Cells may also be constructed such that there are multiple
layers of anodes and
cathodes. Cells may be constructed such that two cathodes are on opposite
sides of a single anode
or vice versa.
A functional or operational battery intended for a specific purpose may
comprise a plurality
of cells arranged according to the needs of particular application. An example
of such a battery is
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19
shown schematically in Figure 3. Here the battery 300 comprises four lithium
cells 100 arranged
in series to increase voltage. Capacity can be increased at this voltage by
providing additional
stacks of four cells 100 in parallel with the stack shown. Different voltages
can be achieved by
altering the number of cells 100 arranged in series.
A positive electrode 306 may be accessible on the outside of a casing 302 of
the battery
300. A negative electrode 304 is also provided. The physical form factor of
the electrodes 304,
306 may vary according to application Various binders, glues, tapes and/or
other securement
mechanisms (not shown) may be employed within a battery casing 302 to
stabilize the other
components. Batteries based on lithium technology are generally operable,
rechargeable, and
storable in any orientation (if a secondary cell). As discussed above, cells
100 may take on various
different geometric shapes. Thus Figure 3 is not meant to represent any
particular physical form
factor of the battery 300.
The battery 300 may also comprise various adjunct circuitry 308 interposing
the positive
electrode 308 and the lithium cells 100 within the casing 302 of the battery
300. In other
embodiments, the adjunct circuitry interposes the negative electrode 304 and
the lithium cells 100
instead of, or in addition to, interposing the positive electrode 306 and the
lithium cells 100. The
adjunct circuitry 308 may include short circuit protection, overcharge
protection, overheating
shutdown and other circuitry as is known in the art to protect the battery
300, the cells 100, and/or
any load attached to the battery 300.
The composition of materials chosen for the cathode 104, anode 106, and
electrolyte may
be critical to the performance of the cell 100 and any battery of which it
forms a part. In the context
of the present disclosure, various examples of AMOs and methods for their
production are
provided in this regard. These AMOs are suitable for use in forming anodes or
cathodes in half
cells, cells, and batteries. The AMOs of the present disclosure are otherwise
compatible with
known lithium cell technology including existing anode and cathode
compositions, electrolyte
formulations, and separator compositions. In other embodiments, the same or
different production,
construction, or formation methods may be employed as are utilized in the case
of AMOs, but with
non-AMO materials.
It will be appreciated that the material of the anode 106 chosen for a cell or
battery
according to the present disclosure may be less electronegative than the
material of the cathode
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104 to suitably complement the cathodic materials. In one particular
embodiment, the disclosed
AMOs are useful as a cathode in a cell having a metallic lithium anode.
In various embodiments of the present disclosure, the cathode 104 comprises an
AMO
material having a surface that is acidic but not superacidic. This would be in
contrast to materials
previously known and utilized as cathodes such as lithium cobalt or lithium
manganese materials.
10
The AMO materials of the present disclosure and methods for their production
are described
below. In other embodiments, the anode 106 comprises an AMO material of the
present disclosure
having a surface that is acidic but not super acidic.
The surfaces of metal oxides are ideally arrays of metal and oxygen centers,
ordered
according to the crystalline structure of the oxide. In reality the arrays are
imperfect, being prone
15
to vacancies, distortion, and the effects of surface attachments.
Regardless, any exposed metal
centers are cationic (positively charged) and can accept electrons, thus
functioning by definition
as Lewis acid sites. Oxygen centers are anionic (negatively charged) and act
as Lewis base sites to
donate electrons. This leads to the well-known amphotericity of metal oxide
surfaces.
Under normal atmospheric conditions, the presence of water vapor will adsorb
to the metal
20
oxide surface either molecularly (hydration) or dissociatively
(hydroxylation). Both OH- and H+
species can adsorb on the oxide surface. The negatively-charged hydroxyl
species will attach at
the metal, cationic (Lewis acid, electron accepting) centers, and the H+ will
attach at the oxygen,
anionic (Lewis base, electron donating) centers. Both adsorptions lead to the
presence of the same
functional group¨a hydroxyl¨on the metal oxide surface.
These surface hydroxyl groups can serve as either Bronsted acids or as
Bronsted bases,
because the groups can either give up or accept a proton. The tendency of an
individual hydroxyl
group to be a proton donor or a proton acceptor is affected by the
coordination of the metal cation
or oxygen anion to which it is attached. Imperfections of the metal oxide
surface such as oxygen
vacancies, or coordination of the surface groups with other chemical species,
mean that all cations
and anions are not equally coordinated. Acid-base sites will vary in number
and in strengths. When
broadly "totaled" across the surface of the oxide, this can give the surface
an overall acidic or basic
character.
The quantity and strength of Lewis acid and base sites (from the exposed metal
cations and
oxygen anions, respectively) and Bronsted acid and base sites (from the
surface hydroxyl groups)
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¨ add broad utility and functionality to the metal oxide and its use in both
chemical reactions and
device applications. The sites are a strong contributor to the chemical
reactivity of the metal oxide.
They can serve as anchor sites to which other chemical groups, and even
additional metal oxides,
may be attached. And they can affect surface charge, hydrophilicity and
biocompatibility.
One way of altering the surface of metal oxides is to attach small chemical
groups or
electron-withdrawing groups ("EWGs") in a process known as surface
functionalization. The
EWG induces polarization of the hydroxide bonds and facilitates dissociation
of hydrogen. For
example, a stronger EWG should lead to a more polarized bond and therefore a
more acidic proton.
The acidity of Lewis sites can be increased by inducing polarization that
facilitates the donation
of electrons to the site. When compounds so made are placed in water, the
acidic protons will
dissociate and so reduce the aqueous pH measurement.
Though somewhat imprecise when working with solid acid/base systems rather
than liquid
ones, traditional methods of pH measurement utilizing titrations, pH paper and
pH probes can be
used to evaluate the acidity of metal oxides dispersed in aqueous solution.
These measurements
can be supplemented by the use of techniques including but not limited to
colorimetric indicators,
infrared spectroscopy, and temperature programmed desorption data to establish
the acidified
nature of the metal oxide surface. Surface groups can be examined by standard
analytical
techniques including but not limited to x-ray photoelectron spectroscopy.
Surface functionalization can be accomplished post-synthesis, including but
not limited to
exposing the metal oxide to acidic solutions or to vapors containing the
desired functional groups.
It can also be accomplished via solid state methods, in which the metal oxide
is mixed and/or
milled with solids containing the desired functional groups. However, all of
these methods require
an additional surface functionalization step or steps beyond those required to
synthesize the metal
oxide itself.
Synthesis and surface functionalization of the AMO material may be
accomplished in a
-single-pot" hydrothermal synthesis method or its equivalent in which the
surface of the metal
oxide is functionalized as the metal oxide is being synthesized from
appropriate precursors. A
precursor salt containing an EWG is solubilized and the resulting solution is
acidified using an
acid containing a second EWG. This acidified solution is then basified and the
basified solution is
heated then washed. A drying step produces the solid AMO material.
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By way of example, a preferred embodiment of an AMO form of tin oxide was
synthesized
and simultaneously surface functionalized using the following single-pot
method:
1. Initially, seven grams (7g) of a tin (II) chloride dihydrate (SnC122H20)
is dissolved
in a solution of 35mL of absolute ethanol and 77 mL distilled water.
2. The resulting solution is stirred for 30 minutes.
3. The solution is acidified by the addition of 7mL of 1.2M HC1, added
dropwise, and
the resulting solution is stirred for 15 minutes.
4. The solution is basified by the addition of 1M of an aqueous base, added
dropwise
until the pH of the solution is about 8.5.
5. The resulting opaque white suspension is then placed in a hot-water bath
(¨ 60 to
90 C) for at least 2 hours while under stirring.
6. The suspension is then washed with distilled water and with absolute
ethanol.
7. The washed suspension is dried at 100 C for 1 hour in air and then
annealed at
200 C for 4 hours in air.
This method results in an A1\40 of tin, surface-functionalized with chlorine,
whose pH is
approximately 2 when resuspended and measured in an aqueous solution at 5 wt%
and room
temperature. By definition its Hammett function, Ho > ¨12. Although an open
system such as a
flask is described here, a closed system such as an autoclave may also be
used.
Utilizing the single pot method disclosed above, a number of AMO's have been
synthesized. Table 1 below describes the precursors and acids that have been
used. In some
instances, a dopant is utilized as well:
Precursor Dopant Acid
SnAc CH3COOH
SnAc H2SO4
SnAc HNO3
SnAc H3PO4
SnAc C6H807
SnAc C211204
SnAc FeAc HC1
SnAc FeAc H2SO4
SnAc FeAc HNO3
SnAc FeAc C211204
SnAc FeAc H3PO4
SnAc FeAc C61-1807
SnAc HBr
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SnAc H3B03
SnSO4 MnC13 H2SO4
SnC12 MnCli HC1
SnC12 FeC13 & AlC13 HC1
FeCl3 SnC13 HC1
Fe(NO3)3 HNO3
BiC13 HC1
Zr(SO4)2 H2SO4
TiOSO4 H2SO4
S132(SO4)3 H2SO4
In(C1)3 HC1
In2(SO4)3 H2SO4
In(III)Br HBr
InC13 HC1
LiAc & FeC13 SnC12 HC1
where Ac is an acetate group with the chemical formula C2H302
In some embodiments, the electron withdrawing groups have a carbon chain
length of 6 or
less and/or an organic mass of 200 or less (AMU). In some embodiments, the
electron withdrawing
groups have a carbon chain length or 8 or less, or 10 or less, and/or an
organic mass of 500 or less.
It will be appreciated that the method's parameters can be varied. These
parameters
include, but are not limited to, type and concentration of reagents, type and
concentration of acid
and base, reaction time, temperature and pressure, stir rate and time, number
and types of washing
steps, time and temperature of drying and calcination, and gas exposure during
drying and
calcination. Variations may be conducted singly, or in any combination,
possibly using
experimental design methodologies. Additionally, other metal oxide synthesis
methods ¨ e.g.,
spray pyrolysis methods, vapor phase growth methods, electrodeposition
methods, solid state
methods, and hydro- or solvo thermal process methods ¨ may be useful for
achieving the same or
similar results as the method disclosed here.
A variety of annealing conditions are useful for preparing AMO nanomaterial.
Example
annealing temperatures may be below 300 C, such as from 100 C to 300 C.
Example annealing
time may range from about 1 hours to about 8 hours, or more. Annealing may
take place under a
variety of atmospheric conditions. For example, annealing may occur in air at
atmospheric
pressure. Annealing may occur at elevated pressure (greater than atmospheric
pressure) or reduced
pressure (less than atmospheric pressure or in a vacuum). Annealing may
alternatively occur in a
controlled atmosphere, such as under an inert gas (e.g., nitrogen, helium, or
argon) or in the
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presence of an oxidizing gas (e.g., oxygen or water).
A variety of drying conditions are useful for preparing A1\40 nanomaterials.
Example
drying temperatures may be from 50 C to 150 C. Example drying time may range
from about
0.5 hours to about 8 hours, or more. Drying may take place under a variety of
atmospheric
conditions. For example, drying may occur in air at atmospheric pressure.
Drying may occur at
elevated pressure (greater than atmospheric pressure) or reduced pressure
(less than atmospheric
pressure or in a vacuum). Drying may alternatively occur in a controlled
atmosphere, such as
under an inert gas (e.g., nitrogen, helium, or argon) or in the presence of an
oxidizing gas (e.g.,
oxygen or water).
The performance characteristics of the AMO nanomaterials of the present
disclosure differ
from those of non-acidified metal oxide nanoparticles. As one example, FIG. 4
shows differences
in the cyclic voltammogram of AMO tin prepared by the single-pot method
relative to that of
commercially available, non-AMO tin when cycled against lithium. For example,
the surface-
functionalized AMO material exhibits better reversibility than the non-AMO
material. The
presence of distinct peaks in the CV of the AMO material may indicate that
multiple electron
transfer steps are occurring during charging/discharging. For example, a peak
at higher voltage
may indicate direct oxidation/reduction of the AMO material, while a peak at
lower voltage may
originate due to changing the material structure of the AMO material (i.e.,
alloying).
As another example, FIG. 5 shows the total reflectance of AMO tin oxide is
different than
that of commercially available, non-AMO tin oxide. The data indicates that the
AMO has a lower
band gap and therefore more desirable properties as a component of a
photovoltaic system in
addition to use as an anode according to the present disclosure.
The AMO material may be thought of as having the general formula
Min0./G
where
MmOx is the metal oxide, m being at least 1 and no greater than 5, x being at
least 1 and no
greater than 21;
G is at least one EWG that is not hydroxide, and
/ simply makes a distinction between the metal oxide and the EWG, denoting no
fixed
mathematical relationship or ratio between the two.
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5 G may represent a single type of EWG, or more than one type of EWG.
Exemplary AlVIOs are acidified tin oxides (Snx0y), acidified titanium dioxides
(Tia0b),
acidified iron oxides (Fec0a), and acidified zirconium oxide (Zre0r).
Exemplary electron-
withdrawing groups ("EWGs") are Cl, Br, B03, SO4, PO4 and CH3C00. Regardless
of the specific
metal or EWG, according to the present disclosure, the AMO material is acidic
but not superacidic,
10 yielding a pH <7 when suspended in an aqueous solution at 5 wt% and a
Hammett function, Ho
> ¨ 12, at least on its surface.
The AMO material structure may be crystalline or amorphous (or a combination
thereof),
and may be utilized singly or as composites in combination with one another,
with non-acidified
metal oxides, or with other additives, binders, or conductive aids known in
the art. In other words,
15 an anode prepared to take advantage of the AMO's of the present
disclosure may or may not
comprise other materials. In one embodiment, the AMO may be layered upon a
conductive
material to form the cathode 104. In some embodiments, the AMO material is
added to a
conductive aid material such as graphite or conductive carbon (or their
equivalents) in a range of
10 wt% to 80 wt% and upwards of 90 wt% to 95 wt%. In preferred embodiments,
the AMO is
20 added at 10 wt%, 33 wt%, 50 wt%, and 80 wt%.
To maximize the amount of overall surface area available, the AMO should be in
nanoparticulate form (i.e., less than 1 micron in size) and substantially
monodispersed. More
preferably, the nanoparticulate size is less than 100 nm and, even more
preferably, less than 20 nm
or 10 nm. In other embodiments utilizing non-AMO metal oxides, the material
may nevertheless
25 be in nanoparticulate form and may be substantially monodispersed.
Again, the nanoparticles size
may be less than 100 nm and preferably less than 20 nm or less than 10 nm.
Mixed-metal AMOs, in which another metal or metal oxide is present in addition
to the
simple, or binary oxide, have been reduced to practice in forming anodes
utilized in half cells,
cells, and batteries. These mixed-metal AMOs may be thought of as having the
general formula
MmNa0x/G and MmNaRrOx/G
where:
M is a metal and m is at least 1 and no greater than 5;
N is a metal and n is greater than zero and no greater than 5;
R is a metal and r is greater than zero and no greater than 5;
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0 is total oxygen associated with all metals and x is at least 1 and no
greater than 21;
/ simply makes a distinction between the metal oxide and the electron-
withdrawing surface
group, denoting no fixed mathematical relationship or ratio between the two;
and
G is at least one EWG that is not hydroxide.
G may represent a single type of EWG, or more than one type of EWG.
Some prior art mixed metal oxide systems, of which zeolites are the most
prominent
example, display strong acidity even though each simple oxide does not.
Preferred embodiments
of the mixed-metal AMO of this disclosure differ from those systems in that
any embodiment must
include at least one AMO which is acidic (but not superacidic) in simple
Mm0x/G form. Preferred
mixed metal and metal oxide systems are SnxFecOy-pd and SnxTia0y+b, where y+d
and y+b may be
an integer or non-integer value.
In another embodiment, the mixed metal AMO material is produced via the single-
pot
method with one modification: synthesis begins with two metal precursor salts
rather than one, in
any proportion. For example, Step 1 of the single-pot method may be altered as
follows: Initially,
3.8 g of tin (II) chloride dihydrate (SnC122H20) and 0.2 g of lithium chloride
(LiC1) are dissolved
in a solution of 20mL of absolute ethanol and 44 mL distilled water.
Metal precursor salts as shown in Table 1 could also be used, in any
proportion. The metal
precursor salts could have the same or differing anionic groups, depending on
the desired product;
could be introduced at different points in the synthesis; or could be
introduced as solids or
introduced in a solvent. In some embodiments, a first metal precursor salt may
be used for the
primary structure (i.e., larger proportion) of the resultant AMO, and a second
(and optionally a
third) metal precursor salt may be added as a dopant or as a minor component
for the resultant
AMO.
Experimentation with the single-pot method led to seven notable findings.
First, in all cases
both surface functionalization and acidity arise endogenously (see FIG. 6),
rather than created
post-synthesis. Unlike prior art surface functionalization methods, the single-
pot method does not
require any additional step or steps for surface functionalization beyond
those required to
synthesize the metal oxide itself, nor does it make use of hydroxyl-containing
organic compounds
or hydrogen peroxide.
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Second, the method is broadly generalizable across a wide range of metal
oxides and
EWGs. Using the methods of the present disclosure, metal oxides of iron, tin,
antimony, bismuth,
titanium, zirconium, manganese, and indium have been synthesized and
simultaneously surface-
functionalized with chlorides, sulfates, acetates, nitrates, phosphates,
citrates, oxalates, borates,
and bromides. Mixed metal AlVIOs of tin and iron, tin and manganese, tin and
manganese and iron,
tin and titanium, indium and tin, antimony and tin, aluminum and tin, lithium
and iron, and lithium
and tin also have been synthesized. Additionally, surface functionalization
can be accomplished
using EWGs that are weaker than halogens and SO4 yet still produce acidic but
not superacidic
surfaces. For example, the method also has been used to synthesize AMOs
surface-functionalized
with acetate (CH3C00), oxalate (C204), and citrate (C6I+02). A variety of
Examples are described
below.
Third, there is a synergistic relationship between the EWG and other
properties of the
nanoparticles such as size, morphology (e.g., plate-like, spherical-like,
needle- or rod-like),
oxidation state, and crystallinity (amorphous, crystalline, or a mixture
thereof). For example,
differences in morphology can occur between AMO nanoparticles synthesized
under identical
conditions except for the use of a different EWG for surface functionalization
(see FIG. 7). The
surface functionalization may act to "pin" the dimensions of the
nanoparticles, stopping their
growth. This pinning may occur on only one dimension of the nanoparticle, or
in more than one
dimension, depending upon exact synthesis conditions.
Fourth, the character of the AMO is very sensitive to synthesis conditions and
procedures.
For example, differences in morphology and performance of the AMO' s
nanoparticles can occur
when synthesized under identical conditions except for having two different
total reaction times
(see FIGS. 8 and 9). Experimental design methodologies can be used to decide
the best or optimal
synthesis conditions and procedures to produce a desired characteristic or set
of characteristics.
Fifth, both the anion present in the precursor salt and the anion present in
the acid contribute
to the surface functionalization of the AMO. In one preferred embodiment, tin
chloride precursors
and hydrochloric acid are used in a synthesis of an AMO of tin. The
performance of these particles
differ from an embodiment in which tin chloride precursors and sulfuric acid
are used, or from an
embodiment in which tin sulfate precursors and hydrochloric acid are used.
Therefore, matching
the precursor anion and acid anion is preferred in some embodiments.
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Sixth, when utilizing a precursor with a weak EWG and an acid with a strong
EWG, or
vice versa, the strongly withdrawing anion will dominate the surface
functionalization. This opens
up a broader range of synthesis possibilities, allowing functionalization with
ions that are not
readily available in both precursor salts and acids. It may also permit mixed
functionalization with
both strong and weak EWGs. In one example, a tin acetate precursor and
phosphoric acid are used
to synthesize an AMO of tin. X-ray photoelectron spectroscopy analysis of the
surface shows a
greater atomic concentration of phosphorous than of the bonds associated with
acetate groups (see
FIG. 10).
Seventh, and last, while the disclosed method is a general procedure for
synthesis of
AMOs, the synthesis procedures and conditions may be adjusted to yield sizes,
morphologies,
oxidation states, and crystalline states as are deemed to be desirable for
different applications. As
one example, catalytic applications might desire an AMO material which is more
active in visible
light (see FIG. 11A) or one which is more active in ultraviolet light (see
FIG. 11B).
In another example, the AMO material may be used as a battery electrode. A
primary
(single-use) battery application might desire an AIVIO with characteristics
that lead to the highest
capacity, while a secondary (rechargeable) battery application might desire
the same AMO but
with characteristics that lead to the highest cyclability. FIG. 12 compares
the cyclability of two
different batteries constructed from AA/10 materials, including a chlorine
containing AA/10 and a
sulfur containing AMO. The AM material can result in enhanced battery
performance, without
deterioration of battery components or gas generation (see FIG. 13). This is
exactly opposite what
the prior art teaches.
In FIG. 13, the charge-discharge cyclability of a battery constructed as a
half-cell of an
AMO nanomaterial electrode versus lithium metal is shown, showing cyclability
for up to 900
charge-discharge cycles, while still maintaining useful capacity and
exceptional columbic
efficiency. Such long cyclability is exceptional, particularly against the
lithium metal reference
electrode, as lithium metal is known to grow dendrites during even low cycle
numbers, which can
enlarge and result in dangerous and catastrophic failure of a battery cell.
According to the present disclosure, in a complete cell, the anode 106
comprising a
disclosed A1\40 may be utilized with a known electrolyte 108 and a cathode 104
comprising known
materials such as lithium cobalt oxide (LiCo02). The material comprising the
separator 110 may
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likewise be drawn from those currently known in the art. In another
embodiment, the anode 106
may comprise a disclosed non-AMO metal oxide with a known electrolyte 108 and
a cathode 104
comprising known materials, and/or constructed according to known methods.
In a complete cell, the cathode 104 comprising a disclosed AMO may be utilized
with a
known electrolyte 108 and an anode 106 comprising known materials such as
carbon on copper
foil, which display less electronegativity than AMO' s of the present
disclosure. The material
comprising the separator 110 and electrolyte 108 may likewise be drawn from
those currently
known in the art as discussed above. In another embodiment, the cathode 104
may comprise a
disclosed non-AMO metal oxide with a known electrolyte 108 and an anode 106
comprising
known materials, and/or constructed according to known methods.
Various layering and other enhancement techniques may be deployed to maximize
capacity
for holding lithium ions for powering the cell 100. It should also be
understood that a battery
based according to the present disclosure can be deployed as a secondary
(e.g., rechargeable)
battery but can also serve as a primary battery. Although the anodes and
cathodes of the present
disclosure lend themselves to a reversible battery chemistry, a cell or
battery constructed as
described herein, may be satisfactorily deployed as a primary cell or battery.
In the battery industry, the word 'formation' is used to denote initial charge
or discharge
of the battery carried out at the manufacturing facility prior to the battery
being made available for
use. The formation process is generally quite slow and may require multiple
cycles directed at
converting the active materials as-manufactured into a form that is more
usable for cell cycling.
These conversions may be alterations of the structure, morphology,
crystallinity, and/or
stoichiometry of the active materials.
Cells and batteries constructed according to the present disclosure, in some
embodiments,
do not require initial formation and therefore are ready to use as primary
cells or batteries. In other
cases, limited or rapid formation may be employed. Moreover, by deploying the
cells and batteries
of the present disclosure as primary cells that are not intended to be
recharged, some of the safety
issues that may be inherent with lithium battery chemistry are mitigated, as
it is known in the art
that the safety issues more frequently arise during battery cycling. However,
following an initial
primary discharge, cells and batteries disclosed herein are optionally
suitable for use as secondary
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battery systems which may undergo many charge-discharge cycles, such as up
to tens, hundreds,
or even thousands of cycles.
In other embodiments according to the present disclosure, the cathode 104
comprises
nanoparticles of tin oxide (Sn02) in non-AMO form. The tin-oxide nanoparticles
may be
substantially monodispersed. Titanium dioxide (TiO2), iron oxide (FeO, Fe2O3,
Fe304), or another
10
metal oxide may be substituted for the tin oxide according to embodiments of
the present
disclosure. Known electrolytes 108, anodes 106, and separators 110, or those
otherwise described
in this disclosure may be utilized with such embodiments.
It will be appreciated that other battery constructions are possible using the
AMO and non-
AMO metal oxides of the present disclosure. For example, a battery may
comprise a first electrode
15
comprising a metal oxide of the present disclosure (possibly in
monodispersed nanoparticulate
form), a second electrode, and an electrolyte positioned between the first
electrode and the second
electrode. As an example, in a lithium ion battery, the first electrode may
operate as a cathode or
an anode. For example, in operation as a cathode, the second electrode may
correspond to lithium
metal, graphite, or another anodic material. As another example, in operation
as an anode, the
20
second electrode may correspond to a LiCo02, LiMn204, LiNi02, or another
cathodic material.
Useful materials for the second electrode include, but are not limited to,
graphite, lithium metal,
sodium metal, lithium cobalt oxide, lithium titanate, lithium manganese oxide,
lithium nickel
manganese cobalt oxide (NMC), lithium iron phosphate, lithium nickel cobalt
aluminum oxide
(NCA), or any combination of these.
25
It will be appreciated that the AMO materials disclosed herein may also be
added as
dopants to conventional lithium ion cell anodes and/or cathodes, such as in
amounts between 0.01
wt. % and 10 wt. %, or for example, an amount of about 1 wt. %, 5 wt. % or 10
wt % of AMO
material in an electrode. The disclosed AMO materials provide an incredible
capacity for storing
lithium atoms and by adding these materials to conventional lithium ion cell
electrodes, the ability
30
of these composite. As one specific example, an electrode comprises LiCo07
and an AMO. As
another example, an electrode comprises a carbonaceous material, such as
graphite, and an AMO.
The metal oxides of the present disclosure may optionally be used with an
acidic
component, such as a binder, an acidic electrolyte, or an acidic electrolyte
additive. This may be
in the context of an anode, cathode, half-cell, complete cell, integrated
battery, or other
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components. The inventors have surprisingly found that including acidic
components and/or
acidic species, such as organic acids or organic acid anhydrides, in a battery
comprising an AMO
material results in an increase in the capacity of versus batteries where the
acidic species are not
included. Again, the prior art teaches against use of acidic species, as these
species may degrade
metal current collectors and housings and cause deterioration in other
electrode components.
As shown in FIG. 14, which provides comparative cyclability data for AMO-based
batteries formed of the same materials and structure except for one having a
standard electrolyte,
one having a basified electrolyte, and one having an acidified electrolyte.
The batteries included
a construction as follows: all cathodes included the same A1\40 material; all
anodes were lithium
metal; the standard electrolyte was a 1:1:1 mix of dimethylene carbonate,
diethylene carbonate,
and ethylene carbonate with 1 M LiPF6; the acidified electrolyte was the
standard electrolyte with
3 wt. % succinic anhydride; the basified electrolyte was the standard
electrolyte with 3 wt. %
dimethylacetamide. All batteries were cycled at the same discharge rate. As
illustrated, the battery
with the acidified electrolyte system exhibits the best cycling ability,
maintaining the highest
capacity over the largest number of cycles.
FIG. 15 provides additional comparative cyclability data for two different
batteries with
the same battery construction including an acidified electrolyte, except that
the AMO material of
one battery is deacidified by washing with a solvent. The batteries included a
construction as
follows: the cathodes included the AMO material; the electrolyte was a 1:1:1
mix of dimethylene
carbonate, diethylene carbonate, and ethylene carbonate with 1 M LiPF6 and 3
wt. % succinic
anhydride; the anodes were lithium metal. The batteries were cycled at the
same discharge rate.
The battery having the acidified AMO material exhibits higher capacity
retention vs. cycle number,
indicating that the acidified surface of the AMO may interact with the
acidified electrolyte,
providing enhanced performance.
At the present time, lithium batteries are perceived to be a safety risk in
certain situations.
For example, airline regulations currently require partial discharge of
lithium batteries that are to
be carried in the cargo hold. Fires have been reported in devices utilizing
lithium batteries resultant
from runaway exothermal reactions. Moreover, lithium fires can be difficult to
extinguish with
popularly deployed fire suppression systems and devices. For these reasons,
lithium containing
compounds rather than metallic lithium is used in many commercial battery
cells.
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Use of lithium containing compounds in an anode, rather than lithium metal,
may, however,
limit the amount of lithium available for reaction and incorporation into the
cathode upon
discharge, and may thus also limit the capacity of such cells. The presently
disclosed AMO
materials, however, show not only large uptake of lithium during discharge but
also enhanced
safety characteristics. For example, when battery cells comprising the AMO
material in a cathode
and a lithium metal electrode are subjected to safety tests, such as nail
penetration tests, shorting
tests, and overvoltage tests, the cells perform well and do not appear to pose
an unacceptable risk
of fire or explosion. This may be because the AMO' s passivate lithium metal
within a cell or
battery. Even using solid or pure lithium as an anode, devices employing AMO'
s of the present
disclosure as a cathode do not appear to pose an unacceptable risk of fire or
explosion. The novel
safety results may also be due to the low operating voltage of cells
constructed according to the
present disclosure, which in some embodiments is < 1.5 V compared to a
traditional lithium ion
operating voltage of >3.0 V.
Several cells were constructed with a cathode comprising an AMO (5n02)
according to the
present disclosure. The cathode was prepared from a composition of the AMO
(Sn02), Ketj en
black (KB), polyvinylidene fluouride (PVDF), and polyaryl amide (PAA) at a
ratio of
63/10/26.1/0.9 by volume. Double-sided layers of this composition were
prepared at 4mg/cm2 per
side. Six of these layers comprised the cathode. The area of the prepared
cathode was 9 x 4 cm2.
A separator was obtained from Targray Technology International, Inc. and
comprised a 25 pm
thick layer of polypropylene. The separator was 9.4 x 4.4 cm2 in area. An
electrolyte was prepared
from 1M LiPF6 in a solvent of ethylene carbonate, diethyl carbonate, and
dimethyl carbonate in a
1/1/1 ratio by volume. The anode was a 50 p.m thick layer of lithium metal of
9.2 x 4.2 cm2 in
area.
Two of the constructed cells were discharged prior to a safety test and found
to have an
actual capacity of 1.7 Ah, and a specific capacity of 1575 mAh/ g Sn02.
FIG. 16 is a plot of temperature and voltage for a cell constructed as
described above and
subjected to a nail penetration test. The test was conducted at room
temperature and no events
(e.g., fires) were observed It can also be seen that the temperature and
voltage remained stable.
FIG. 17A is a plot of temperature and voltage for a cell constructed as
described above and
subjected to an overcharge test. A 1A current was applied. Apart from some
gassing from the cell
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no adverse events were observed over the timeframe of the test. FIG. 17B is a
plot of the
overcharge test of FIG. 17A focusing on the start of the test.
It should be understood that the examples constructed for purpose of
penetration tests are
not intended to be limiting with respect to the entire disclosure herein.
Cells and batteries of
various sizes, capacities, and materials may be constructed according to the
present disclosure.
Utilizing the AMO' s of the present disclosure, such batteries would reap the
benefits of the
increased safety demonstrated herein, whether such safety is ultimately due to
lithium passiyation,
lower voltage, or other factors.
Embodiments of constructed electrochemical cells incorporating AMO material as
a
cathode and lithium as an electrode have been tested to successfully undergo
up to 900 or more
charge-discharge cycles without resulting in catastrophic and destructive
failure. Stated another
way, embodiments of constructed electrochemical cells incorporating AMO
material as a cathode
and lithium as an electrode have been tested to successfully undergo up to 900
or more charge-
discharge cycles and still hold a charge and maintain useful capacity.
Without wishing to be bound by any theory, the enhanced safety provided by use
of AMO-
based cathode materials in lithium cells may arise from the ability of the AMO
material to passivate
metallic lithium and prevent dendrite formation. The inventors have observed
that, upon cycling,
the metallic lithium anode did not appear to grow or otherwise form dendrites,
but the metallic
lithium anode took on a softer and less crystalline appearing structure. In
some embodiments, the
metallic lithium anode may be passiyated, such as by cycling as a component of
an electrochemical
cell as described herein, and then removed from the electrochemical cell and
used as an electrode
in a new electrochemical cell with a different cathode. Additionally, cells
constructed according
to the present disclosure make use of low operating voltages, such as between
1 and 2 volts, which
contrasts with the typical voltage of a lithium or lithium-ion battery cell,
which operate commonly
around 3-4.2 volts. Such a difference in operational voltage may, in part,
account for the safety of
the disclosed cells.
With respect to construction of cells or batteries using lithium as an anode
according to the
present disclosure, in some embodiments, the entire anode (100%) is metallic
lithium. The
metallic lithium may only be substantially pure in that a minute percentage of
the anode may
comprise trace elements and impurities that do not affect the performance of
the cell or battery in
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a measurable way. In various embodiments, the anode comprises at least 50%,
55%, 60%, 65%,
75%, 80%, 85%, 90%, or 95% metallic lithium.
For purposes of the present disclosure the term "metallic lithium- refers to
lithium in its
neutral atomic state (i.e., non-ionic state). The term metallic lithium is
intended to distinguish over
other forms of lithium including lithium ions and lithium compounds. The term
metallic lithium
may refer to neutral atomic lithium present in mixtures that comprise lithium
atoms, such as
mixtures of lithium and other elements, compounds, or substances. The term
metallic lithium may
refer to neutral atomic lithium present in lithium alloys, such as a metallic
mixture including
lithium and one or more other metals. The term metallic lithium may refer to
neutral atomic
lithium present in composite structures including lithium and one or more
other materials.
Electrodes comprising or including metallic lithium may include other
materials besides lithium,
but it will be appreciated that metallic lithium may correspond to an active
material of such an
electrode. In some cases, an anode in an electrochemical cell comprises
metallic lithium.
For purposes of this disclosure, metallic lithium may be taken to mean lithium
that is not
reacted with any other element so as to have formed a compound (at least at
the time of battery or
cell construction). In some embodiments, a portion of the anode may be
metallic lithium while a
portion of the anode may be a lithium compound containing various percentages
of lithium that is
reacted with other elements to form a lithium compound. The metallic lithium
may be arranged
to be segregated geometrically on or in the anode relative to the lithium
compound portion of the
anode.
Referring now to FIG. 18, a perspective view of a cathode 1800 according to
aspects of the
present disclosure is shown. FIG. 18 is not to scale. The cathode 1800
comprises 33.3% SnO2 in
AMO form. The AMO was prepared according to the methods disclosed above. To
form a carbon
layer 1804 a slurry of Ketjenblack EC-300J (SA: - 800 m2/g) prepared using NMP
solvent and
coated on copper foil 1802 of thickness 10 p.m. The slurry composition was 80%
Ketjenblack and
20% PVDF by weight. As coated tape was dried in a vacuum oven at 100 OC.
To form a carbon/SnO2 layer 1806 SnO2 (AMO), Ketjenblack and PVDF each 33.3%
by
weight were mixed together and slurry was prepared by adding NMP solvent and
coated on part
of the Ketjenblack coated copper foil (1802, 1804). The resultant tape was
dried in a vacuum oven
at 100 C (overnight) and calendared at room temperature. Thickness of the
tape was measured
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5 using a micrometer at SnO2 coated and Ketjenblack (only) coated areas.
The thickness of the
Ketjen black layer 1804 is about 8 p.m; the thickness of the electrode layer
1806 is about 2 p.m.
The foil layer 1802 is about 10 p.m giving a total thickness of the cathode
1800 of about 18 m.
The calendared tape was punched out into circular discs at Ketjenblack (only)
and SnO2
coated areas. The weight of the Ketjenblack disc was subtracted from the SnO2
disc to obtain total
10 mass of the electrode material. In case of one tested cell type, the
total mass of the electrode
material is 0.0005 g (after subtracting the Ketjenblack disc weight), and the
active material content
is 0.000167 g (33.3% of total mass).
Some important elements of the cathode 1800 are (1) layering, using a carbon
undercoat
(2) the use of Ketjenblack high surface area carbon in both undercoat and
topcoat (3) the 33%
15 active material topcoat, and (4) the thin (-2 um) topcoat layer. All of
these parameters may be
further developed.
In some embodiments, carbons other than Ketjenblack are used. Binders other
than PVDF
may be used. The cathode may be constructed in one or more layers. The
percentage of active
material may be more or less than 33%. The thickness of the one or more layers
may be more or
20 less than 2 um. A variety of current collectors may be used in order to
optimize cell construction.
It should be understood that the example above provides one instance of lower
active
material loading within the electrode than has heretofore been believed to
promote optimal
performance and capacity. As previous discussed, traditional preferences for
active loading are
90%, 95%, or more where possible. According to the present embodiment, active
loadings may
25 be less than 80% w/w. In some embodiments, calculation of the active
loading percentage may be
a total active loading that includes various conductive layers of the
electrode. For example, a layer
with a higher (but still low according to prior art teachings) active material
loading of 33% may
provide a total active loading across the electrode of 23% when combined with
the conductive
layer that contains little or no active material. In various embodiments, the
total active material
30 loading of the electrode is less than 63% maximum. In another
embodiment, the active material
loading in total is between 23% and 33%. In yet another embodiment, the active
material loading
in total is between 11% and 14%.
Specific energy densities exhibited by materials according to the present
disclosure (e.g.,
AMO SnO2) are on par with those of fossil fuels. This is taught to be
impossible by prior art
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36
scientific literature. The same effects are observed even with non-AMO metal
oxides (e.g., tin
oxide, titanium dioxide, and or iron oxide) when constructed as electrodes and
batteries according
to methods of the present disclosure. This suggests that the operational
mechanism of these
materials as active materials is outside of that currently known or taught.
As described herein, non-AMO metal oxides may be constructed as electrodes
with an
active material loading that is substantially lower than taught by the prior
art. For example, the
active loading may be below 50%, such as 30-40% by weight, 20-25% by weight,
or particularly
21% or 33% by weight. Formation of an electrode may be by repeated application
of multiple
layers of the active material until a desired thickness is reached. Conductive
carbon may be layered
with the active material as well. The conductive carbon may be applied at the
same or different
loading density as the active material. For example, the active material and
the conductive carbon
may both be present at 20-25%, for example, at 21% by weight In some
embodiments, it has been
determined that application of the active material in multiple thin layers
provides enhanced
performance over a single thicker layer.
Referring now to FIG. 19 a bar graph comparing lithiation capacities of
various metal
oxides using standard construction techniques compared to construction
techniques according to
the present disclosure is shown. High active material loading and other
standard construction
techniques were used in the first instance for AMO tin oxide, AMO iron oxide,
and non-AMO tin
oxide. The AMO tin oxide particle size was on the order of 5 nm. The non-AMO
tin oxide particle
size was on the order of 20 nm.
The AMO tin oxide when utilized with standard construction techniques yielded
a lithiation
capacity of about 2000 mAh/g. When constructed as an electrode with lower
active material
loading (e.g., around 21% by weight) in a layered arrangement with
nanoparticulate conductive
carbon (also around 21% by weight), lithiation capacity increased to over
10,000 mAh/g. The
increase using AMO iron oxide when subjected to the same test was from
slightly less than 2000
mAh/g to around 8000 mAh/g. Non-AMO tin oxide, surprisingly, also increased
from less than
2000 mAh/g to more than 6000 mAh/g. The average increase using the high
capacity construction
method was about 314%.
According to embodiments of the present disclosure, blends of materials may be
utilized
as actives in constructions of electrodes (e.g., anodes and/or cathodes),
cells, and batteries. In
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accordance with exemplary embodiments, AMOs of the present disclosure, such as
tin oxide AMO
may be blended with materials such as LiC002, FeS2, Mn02 and/or other known
battery active
materials for increases in performance.
The AMOs may be blended with non-acidified metal oxides according to methods
that are
known in order to produce active materials for use in battery electrodes and
for other applications.
The AMOs may be blended with the non-acidified metal oxides by simple
mechanical mixing or
by milling. Mechanical mixing or milling can be performed in either dry or wet
conditions. They
may be blended with the aid of appropriate surfactants to control and enhance
uniformity and
dispersion of the mix. The blends may be used as dry materials or as wet
suspensions. The blends
may be used to form electrodes by being pressed, cast from slurries, or
printed.
FIG. 20 is a graph of voltage versus energy for Mn02 as an active material
blended with
varying amounts of AMO tin according to the present disclosure. A baseline of
only Mn02 as an
active is shown, as well as blends incorporating 2, 5, and 8% tin oxide A_MO
according to the
present disclosure. As can be seen, all blends provide increases in energy. As
little as 8% of the
A1\40 according to the present disclosure provide over a 50% energy increase.
As previously mentioned metal oxides are expected to be basic, and in
particular metal
oxides used as battery active materials are known to be basic. The enhancement
of energy density
by blending an acidic material with a neutral or basic one is unexpected. It
runs counter to
generally accepted chemical ideas that acids and base neutralize one another,
thereby removing
the unique performance characteristics that either the acid alone or the base
alone might provide.
It is a particularly unexpected result that the presence of acidic and basic
components would have
a positive and synergistic effect. However, the degree of positive effect and
optimum ratio
between AMO and non-AMO actives is not necessarily linear or predictable. In
each blend of an
individual AMO with one of many potential types of non-AMO active, an optimum
point for
enhanced energy density must be determined experimentally. Nevertheless, the
benefits can be
observed across a wide range of actives. The blends and ranges tested and
illustrated in FIG. 20
are exemplary. In other embodiments the AMO may range from <1%, 1-5%, 5-10%,
10-20%, 10-
30%, 30-40%, 50-99%, or >99% of the active material. In some embodiments, the
precise ratio
may be derived based upon desired cost vs. energy of the final product (e.g.,
material, electrode,
cell, battery, etc.).
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The precise ratio (AMO/non-AMO) may also be derived based upon the type, size,
and
physical/mechanical characteristics of the electrode that must be formed. The
precise ratio may
also be derived based upon desired electrical performance. Lower ratios of AMO
to non-AMO
show voltage profiles that are more similar to the voltage profile of the non-
AMO alone. Higher
ratios show voltage profiles that are more similar to the voltage profile of
the AMO alone. This
gives the AMO/non-AMO blends a unique tunability to target specific electronic
use cases that
does not currently exist in the battery industry. The precise ratio of AMO to
non-AMO for any
given application, therefore, represents a unique blend of desired electrical
performance, energy
density, and cost.
The Applicant has tested a number of different AMO and non-AMO blends and
found
positive effects by addition of various AMO' s according to the present
disclosure with non-AMOs
such as lithium manganese oxides, lithium manganese nickel oxides and
manganese nickel oxides.
Blending methods have also been shown to work with lithium titanium oxides and
titanium oxides;
lithium iron phosphates and iron phosphates; lithium nickel cobalt aluminum
oxides and nickel
cobalt aluminum oxides, and lithium nickel manganese cobalt oxides and nickel
manganese cobalt
oxides. It should also be understood that the AMO/non-AMO blends of the
present disclosure
have been determined to be useful in both primary and secondary applications
with performance
enhancements observed in each.
In some embodiments, an electrode or an active material blend consists only of
the
identified AMO and non-AMO. In some embodiments, the active materials of the
electrode
consist only of the identified AMO and non-AMO but may have additional
carbons, conductors,
and non-active ingredients included in the electrode. In other embodiments, an
electrode or active
material blend may contain the identified AMO and non-AMO as well as other
materials as are
known in the art.
In further embodiments, AMO' s according to the present disclosure may be
incorporated
into or blended with active materials used in so-called alkaline batteries.
Such battery chemistry
finds wide application in standard battery sizes such as "AA", "AAA", "C", "D"
and other standard
sized batteries that consumers are familiar with. Typically, such batteries
are primary discharge
batteries when used with standard alkaline chemistry. However, the present
disclosure and AMO-
alkaline blended active material may find application in primary and secondary
discharge systems.
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Referring now to FIG. 21, a side cutaway view of an exemplary battery 2200
based on
alkaline chemistry is shown. The battery 2200 may comprise a positive terminal
2202 spaced apart
physically from a negative terminal 2204. An anode 2206 may be electrically
connected to the
negative terminal 2204 via current collector 2208. A cathode 2210 is spaced
apart from the anode
2206 by separator 2212 and electrically connected to the positive terminal
2202. Some
embodiments include a protective end cap 2214 retaining the internal
components in their proper
location within an outer casing 2216 without inducing shorts (e.g., the end
cap 2214 may be non-
conductive and resistant to degradation by any of the internal battery
chemistry). Other physical
features such as ventilation holes and other safety and structural components
as are known in the
art may be included but are not shown for simplicity.
Referring now to FIG. 22, an alkaline cell comprising an acidified SnO2 of
this disclosure
10 wt% blended with manganese dioxide (the rest of the cell being a Zn anode
and an alkaline
(basic) electrolyte)), shows improved discharge capacity compared to a
traditional alkaline
electrode. In prior art alkaline chemistry, an anode may comprise a zinc-based
material such as
zinc powder and a basic electrolyte such as potassium hydroxide electrolyte. A
prior art cathode
may comprise manganese dioxide (Mn02) possibly blended with carbon powder.
Other
chemistries may incorporate lithium so as to provide a lithium manganese oxide
(LMO) cell or
battery and a carbonate electrolyte. According to embodiments of the present
disclosure, the anode
2206 may comprise zinc and may also contain an electrolyte such as potassium
hydroxide. The
cathode 2210 may comprise manganese dioxide or LMO blended or combined with
AMOs as
disclosed herein.
The percentage of AMO that may be blended with the Mn02 or LMO or other
alkaline
chemistry material may range from 1-99%, with ranges of 1%, 2%, 5%, 8%, 10%,
and 12% as
exemplary embodiments. The 8-14% range may be most efficacious in terms of
improved
performance of the final battery or cell in view of the amount of AMO
incorporated.
Although the examples discussed above are in terms of a battery or cell that
may find use
in place of AA, AAA, C, and/or D cells, the use of the AMOs of the present
disclosure in blends
with traditional alkaline chemistry is not limited to those specific examples
or applications. For
example, blends of AMOs of the present disclosure can be utilized in button
cells, standard 9V
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5 batteries, and other form factors. Additionally, the AMO may be
incorporated with the manganese
or LMO cathode material in a slurry cast, tape cast, pressed pellet, pressed
ring or other building
process. All references throughout this application, for example patent
documents including issued
or granted patents or equivalents, patent application publications, and non-
patent literature
documents or other source material, are hereby incorporated by reference
herein in their entireties,
10 as though individually incorporated by reference.
All patents and publications mentioned in the specification are indicative of
the levels of
skill of those skilled in the art to which the invention pertains. References
cited herein are
incorporated by reference herein in their entirety to indicate the state of
the art, in some cases as
of their filing date, and it is intended that this information can be employed
herein, if needed, to
15 exclude (for example, to disclaim) specific embodiments that are in the
prior art. For example,
when a compound is claimed, it should be understood that compounds known in
the prior art,
including certain compounds disclosed in the references disclosed herein
(particularly in
referenced patent documents), are not intended to be included in the claim.
When a group of substituents is disclosed herein, it is understood that all
individual
20 members of those groups and all subgroups and classes that can be formed
using the substituents
are disclosed separately. When a Markush group or other grouping is used
herein, all individual
members of the group and all combinations and subcombinations possible of the
group are
individually included in the disclosure. As used herein, "and/or" means that
one, all, or any
combination of items in a list separated by "and/or" are included in the list;
for example, "1, 2
25 and/or 3" is equivalent to "1' or '2' or '3' or '1 and 2' or '1 and 3'
or '2 and 3' or '1, 2 and 3'".
Every formulation or combination of components described or exemplified can be
used to
practice the invention, unless otherwise stated. Specific names of materials
are intended to be
exemplary, as it is known that one of ordinary skill in the art can name the
same material
differently. One of ordinary skill in the art will appreciate that methods,
device elements, starting
30 materials, and synthetic methods other than those specifically
exemplified can be employed in the
practice of the invention without resort to undue experimentation. All art-
known functional
equivalents, of any such methods, device elements, starting materials, and
synthetic methods are
intended to be included in this invention. Whenever a range is given in the
specification, for
example, a temperature range, a time range, or a composition range, all
intermediate ranges and
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subranges, as well as all individual values included in the ranges given are
intended to be included
in the disclosure.
As used herein, "comprising- is synonymous with "including," "containing," or
"characterized by," and is inclusive or open-ended and does not exclude
additional, unrecited
elements or method steps. As used herein, "consisting of' excludes any
element, step, or ingredient
not specified in the claim element. As used herein, "consisting essentially
of' does not exclude
materials or steps that do not materially affect the basic and novel
characteristics of the claim Any
recitation herein of the term "comprising," particularly in a description of
components of a
composition or in a description of elements of a device, is understood to
encompass those
compositions and methods consisting essentially of and consisting of the
recited components or
elements. The invention illustratively described herein suitably may be
practiced in the absence
of any element or limitation that is not specifically disclosed herein.
The terms and expressions which have been employed are used as terms of
description and
not of limitation, and there is no intention in the use of such terms and
expressions of excluding
any equivalents of the features shown and described or portions thereof, but
it is recognized that
various modifications are possible within the scope of the invention claimed.
Thus, it should be
understood that although the present invention has been specifically disclosed
by preferred
embodiments and optional features, modification and variation of the concepts
herein disclosed
may be resorted to by those skilled in the art, and that such modifications
and variations are
considered to be within the scope of this invention as defined by the claims.
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