Note: Descriptions are shown in the official language in which they were submitted.
CHEMICAL SYNTHESIS ROUTE FOR LITHIUM ION BATTERY APPLICATIONS
[0001]
TECHNICAL FIELD
[0002] The present disclosure is generally concerned with processing
techniques
for materials synthesis for lithium ion batteries.
BACKGROUND
[0003] Conventional LiMnPO4 material is a material exhibiting low electrical
conductivity. As a result, this material is restrictive or picky on the
synthesis conditions
and electrode preparation methods for lithium ion battery applications. Even
though
carbon coating has been used to improve the electrochemical property, carbon
coating
alone may not resolve the intrinsically low electrical conductivity nature of
the LiMnPO4
material. Furthermore, the carbon coating may limit the storage time of the
resultant
material, and the coating nature may be destroyed during the slurry making
process
especially when solvent is water based. Since coating is on the material
surface only,
the integrity of the coating is always challenged during the electrode making
processes
and this increases the chance of unstable (inconsistent) performance of the
final
battery.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Many aspects of the disclosure can be better understood with reference
to the
following drawings. The components in the drawings are not necessarily to
scale, emphasis
instead being placed upon clearly illustrating the principles of certain
embodiments of the
present disclosure. Moreover,
in the drawings, like reference numerals designate
corresponding parts throughout the several views.
[0005] FIG. 1 is a flow chart diagram illustrating an embodiment of an
exemplary
process for materials synthesis for lithium ion batteries in accordance with
the present
disclosure.
[0006] FIG. 2 is a diagram of an exemplary embodiment of a furnace and a heat
treatment environment for the synthesis of materials in accordance with the
present
disclosure.
[0007] FIG. 3 is a diagram illustrating the result of an examination of
synthesized
materials using X-ray diffraction in accordance with embodiments of the
present disclosure.
[0008] FIG. 4 is diagram of examination results for the charge capacity of
synthesized
materials in accordance with embodiments of the present disclosure.
[0009] FIG. 5 is a diagram illustrating a result of an examination of
synthesized
materials using X-ray diffraction in accordance with embodiments of the
present disclosure.
DETAILED DESCRIPTION
[00010] Disclosed herein are certain embodiments of a novel chemical synthesis
route
for lithium ion battery applications. In one such embodiment, battery active
material
LiMn204 is used as a starting precursor. Accordingly, a new synthesis
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route is disclosed showing how to make LiMnPO4 composite materials at low
temperatures using LiMn204 as the synthesis precursor. By doing so, a
resulting
material's electrical conductivity is enhanced with the presence of residual
LiMn204.
Further, with the aid of a synthesis route of phosphate material at low
temperatures,
it is possible to synthesize materials with dual battery active material, thus
achieving
the possibility in tailoring physical and electrochemical properties of the
synthesized
materials. In addition, embodiments of the present disclosure contemplate and
allow
for multiple-active-material materials systems in battery applications.
[00011] In accordance with the present disclosure, spinel structured LiMn204
may be used as the precursor material, in various embodiments. Consider that
since
the spinel structured LiMn204 is stable at high temperatures, it is easy to
synthesize
mixed oxide phosphate material using spinel structure material as the
precursor. For
example, the synthesis of Li(Mn1/2Fe1/2)PO4 can be achieved using
Li(Mn1/2Fe1/2) 204 as the starting precursor.
[00012] Additionally, for various embodiments, control of phosphorous content
may determine the ratio of the precursor to the resultant material. This may
be useful
in tailoring the electrical conductivity as well as the electrochemical
capacity of the
resultant material. For example, easy control of the phosphorous content in
the
resultant material renders flexibility in tailoring a final material's
physical and
electrochemical properties.
[00013] As discussed below, an embodiment of a new synthesis route is
disclosed showing how to make LiMnPO4 or LiMnPO4-LiMn204 composite
materials at low temperatures (e.g., less than 4000C, and can be as low as
120oC)
using LiMn204 as the synthesis precursor. Low temperature synthesis offers the
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chance in maintaining the precursor materials structure (and thus maintain
electrochemically active) in the resultant material.
[00014] In general, an embodiment of a process for the new materials synthesis
contains several important steps as shown in FIG. 1. The process starts with
the
leaching of LiMn204 using acids, in step 102. Next, carbonaceous materials
that
decompose at elevated temperatures are added, in step 104. Here, elevated
temperatures are meant to include temperatures which are sufficient in
decomposing the carbonaceous materials thus increasing the materials
conductivity.
[00015] Referring back to the figure, the synthesized material is partially
converted to LiMnPO4, in step 106; and a proper amount of Li containing
compound
is added, in step 108, as discussed further below. Then, the synthesized
material is
dried using a furnace under air or oxygen atmosphere, in step 110, to produce
or
generate the resulting material, in step 112.
[00016] FIG. 2 shows the design of a furnace and a heat treatment environment
for the synthesis of the materials presently disclosed. FIG. 2 shows reaction
vessel
1, which is open to air in furnace 2. The furnace is open to the atmosphere at
3a
and 3b so as to maintain substantially atmospheric pressure in the furnace.
Flow of
gases into or out of the furnace is dependent on heating and cooling cycles of
the
furnace and chemical reactions taking place with materials in the furnace. Air
is free
to enter the furnace, and air and/or products of a chemical reaction of
materials 4 in
the reaction vessel 1 are free to exit the furnace. Materials 4 in vessel 1
react
chemically during heating steps to form cathode materials in accordance with
the
present disclosure. Materials 4 in vessel 1, which face air found in the
furnace, are
covered by a layer of a high temperature inert blanket 5, which is porous to
air and
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escaping gases caused by the heating step. Heating coils of the furnace are
indicated at 6.
[00017] The following are examples of synthesis routes in accordance with
embodiments of the present disclosure.
EXAMPLE 1
Synthesis of LiMnPO4-LiMn204 = 1.8:0.1 in molar ratio (equivalent to 95 moll%
of
LiMnPatand 5 mol% of LiMn204)
[00018] The overall reaction can be simply described below as:
[00019] 1 LiMn204 + 1.8 H3PO4 + 0.9Li ------------------------------ >
1.8LiMnPO4 + 0.1 LiMn204 + (H
and 0) .
[00020] Exemplary synthesis procedures are detailed as below:
1. Initially, dissolve oxalic acid (e.g., 22.5g) (0.25 mole) in CMC
(carboxymethyl cellulose 1 wt% solution) 40g at 60 C.
2. Add LiMn204 (e.g., 181g) (1 mole) to the solution. At this time, purplish
foam evolves implying the dissolution of Mn into the solution. Keep the
solution at 80 C for two hours until reaction is completed.
3. Add proper amount of carbonaceous materials. In this exemplary case,
sucrose (e.g., 67.5g) is added into the solution.
4. Then, cool down the solution using ice bath.
5. Then, add phosphoric acid (e.g., 207g) (1.8 mole, 85% in H3PO4 content)
to the solution slowly (in two hours) in ice bath.
6. Then, warm the solution to 50 C for two hours (at this moment, greenish
powder forms).
7. Cool the solution again and add (e.g., 50g) (1.1 mole) formic acid.
Afterwards, add Li2CO3 (e.g., 33.3g) (0.9 mole in Li content) to the solution.
CA 2956031 2018-08-03
While adding Li2CO3 to the solution, bubbles form and the solution became a
slurry.
8. After Li2CO3 addition, the slurry temperature is raised again to 50 C. At
this
time, foaming is observed.
9. After 2 hours foaming, the very viscous solution is dried at 120 C for 10
hours.
[00021]
Step 1 and 2 (above) are used for leaching Mn from LiMn204. The acid
used in step 1 is not limited to oxalic acid. Formic acid, acetic acid,
hydrochloric acid,
nitric acid are all allowed. However, organic acids are preferred in some
embodiments.
[00022]
Step 3 (above) is used in carbonaceous material addition. The
carbonaceous material is not limited to sucrose. Methyl cellulose (MC),
Methylcarboxylmethyl cellulose (MCMC), Cellulose acetate, starch, styrene
butadiene
rubber are all allowed in achieving the same goal (i.e. increase material's
electrical
conductivity after decomposition). In fact, the materials synthesis can be
free from
the addition of the carbonaceous material if proper amount and distribution of
LiMn204 are present in the resultant material.
[00023]
Steps 4, 5, and 6 (above) are used for MnPO4 formation. These steps
control the percentage of LiMn204 remaining or the percentage of MnPO4
formation. Steps 7, 8, and 9 are used for the formation of LiMnPO4 in the form
of
foam. Foaming can be helpful in making materials with open porosity.
[00024] For
comparative analysis, the resultant material was examined with XRD
(X-ray Diffraction) and the XRD result is shown in FIGS. 3A-3B. Rietveld
refinement
was conducted on the XRD result using space group Pmnb(62). The lattice
parameters were determined to be a = 6.10287, b = 10.4603, and c = 4.74375
with
6
DaWkiNthate Received 2020-12-16
=
Phase #1 [Bragg-F. = 2-45%]: lAtieltIglile
Chemical Form-ula = LalstinP044-'
Orthorhombic: Vxnnl (62), Z=4, 91)? (PDF#00-033-080334-'
+-f
[x] 610287 (0.00265) <2> I = 90.0
(0.0 ) <2>4)
(x] bõ,õ..õ7. 104603 (0.00438) <2> f fs =9410 (0.0 )<2>,,,,
= 4.74375 (000223) <2> []y = 90.0 (0,0 )
4-,
Unit Cell Nblume = 302_8(k), Density = 3.4401(Wan'),4kuntig. n(p) =
410.0(1icm)4-'
4-1
(x3 SF = 31,2795 (03038.1) <1> Intensity Scale Factero
(11F 00 (0.0 ) <4> Overall Temperature F'actur (Ctrl: All
Pliases)o
[]TS =410 (0.0 ) ,e-4> Thin Specimen Absorption
Correct:kiwi
(3 PO = 1.0 (0.0 ) <3> Preferred Oyientation Correctiono
[..c3 =0.13593 (0.01862) <"P,- FW1114= f0 x 2e+Q x24)
=012464 (0.03578) <3>4-'
[]f2 = 0.0 (0.0 ) <3>4-'
Reimement Halted (R,T=1,32), Round=3, Iter--7, .P=31, It:=2.45% (E=1.86%,
EPS9_5:(4-1
Rietveld refinement was conducted on the XRD result using space group
Pmnb(62). The lattice parameters were determined to be a = 6.10287, b =
10.4603,
and c =4.74375 with
6a
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cell volume =302.8 (A3) and Density = 3.4401 g/cm3. In this case, the trace
phase of
LiMn204 is not obvious in the XRD plot. The particle size and BET analyses on
the
precursor LiMn204 and the resultant material are also shown in Table I for
comparisons of the evolution of physical properties exhibited by the material
during
the synthesis route.
Table I
Particle size Data (urn) Surface Area
Data (BET)
010 D50 0100 (m2/g)
LiMn204 2.88 15.97 71.08 0.6368
Resultant 0.78 2.39 44.60 1.2556
Material t
After Heat 0.86 2.81 60.03 2.35
Treatment
T Resultant material was obtained after drying the sample at 120 C for 10
hours.
After heat treatment refers to 260 C for 2 hours.
[000251 From Table I, it can be seen that pulverization of the precursor
material
occurred during the synthesis. The particle size decreased with the increase
of
specific surface area. A further heat treatment of the resultant material at
260 C for 2
hours in air shows that a moderate increase of particle size is accompanied
with
significant increase of specific surface area (please refer to Table 1). This
result
indicates that sintering of the material is not rigorous at 260 C but the
decomposition
of the carbonaceous material is contributing to the significant increase of
the specific
surface area. It should be noticed that the decomposition at 260 C could help
material's electrical conductivity owing to the presence of the electrical
conducting
carbon resulted from the carbonaceous materials decomposition.
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EXAMPLE 2
Electrochemical characterization of LiMnPO4-LiMn204 = 1.8:0.1 in molar ratio
(equivalent to 95 mol% of LiMnPO4and 5 mol% of LiMn204)
[00026] For electrode preparation, 5g of active material, 1g of Super-P carbon
black, and 0.3g of SBR (styrene-butadiene rubber) are used in the slurry
making. After
coating using doctor blade, the coated electrode is dried at 110 C for 3 hours
followed
by punching of the electrode. After vacuum drying again at 110 C for
overnight, the
electrodes are transferred to the glove box for test cell assembly. The test
cell is a
three-electrode design with Li as the reference electrode. The electrode
loading is
6mg and the active material content is 81.3%. The C-rate used is around C/10
and
the room temperature is around 23 C.
[00027] A charge capacity of 160.5mAh/g and a discharge capacity of 51mAh/g
are
obtained, as shown in the examination results of FIG. 4. The corresponding
Coulomb
efficiency is observed to be 31.7%. Since the test cell was charged to 4.9V,
more or
less decomposition of the electrolyte during charging could result in the low
Coulomb
efficiency.
EXAMPLE 3
Synthesis of LiMnPO4-LiMn204 = 1:0.5 in molar ratio (equivalent to 67 mol% of
LiMnPO4 and 33 mol% of LiMn204)
[00028] The overall reaction can be simply described below as:
1 LiMn204 + 1 H3PO4 --------- > 1Li(1-0.5x)MnPO4+ 0.5 LixMn204 , where
X represents deficiency of Li. Exemplary synthesis procedures are detailed as
below:
1. Initially, dissolve oxalic acid (e.g., 11.25g) (0.125 mole) in CMC
(carboxymethyl cellulose 1wt% solution) (e.g., 40g) at 80 C.
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2. Add LiMn204 (e.g., 90.5g) (0.5 mole) to the solution. At this time,
purplish
foam evolves implying the dissolution of Mn into the solution. Keep the
solution at 80 C for two hours until reaction is completed.
3. Add proper amount of carbonaceous materials. In this exemplary case,
sucrose (e.g., 33.75g) is added into the solution.
4. Then, cool down the solution using ice bath.
5. Then, add phosphoric acid (e.g., 57.65g) (0.5 mole, 85% in H3PO4 content)
to the solution slowly (in two hours) in ice bath.
6. Then, warm the solution to 50 C for two hours (at this moment, greenish
powder forms).
7. Wait until the solution become tacky.
8. Conduct heat treatment by sending the precursor material directly to the
furnace at 380 C for 10 hours under oxygen.
[00029] For comparative analysis, the resultant material was examined with XRD
and the XRD result is shown in FIG. 5. From the XRD result, it can be
identified that
the resultant material consists of two phases (LiMnPO4 and LiMn204 co-exist),
which are present simultaneously.
[00030] Until this point, it is clear that the low temperature synthesis in
accordance with embodiments of the present disclosure allows the co-existence
of
LiMnPO4 and LiMn204. The electrochemical data reveals the potential in
synthesizing LiMnPO4 with the presence of LiMn204 using LiMn204 as the
starting
precursor. Advantageously, the presence of LiMn204 in the LiMnPO4/LiMn204
composite material provides electrochemical activity as well as the electrical
conducting capability in the composite material. Exemplary composite material
for
lithium ion battery applications in accordance with the present disclosure may
be in
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the form of (x)LiMnPO4/(1-x)LiMn204, where x ranges from 0.67 mol% to 0.99
mol%.
[00031] Any process descriptions or blocks in flow charts should be understood
as
representing steps in an exemplary process, and alternate implementations are
included within the scope of the disclosure in which steps may be executed out
of
order from that shown or discussed, including substantially concurrently or in
reverse
order, depending on the functionality involved, as would be understood by
those
reasonably skilled in the art of the present disclosure.
[00032] It should be emphasized that the above-described embodiments are
merely
possible examples of implementations, merely set forth for a clear
understanding of
the principles of the disclosure. Many variations and modifications may be
made to
the above-described embodiment(s) without departing substantially from the
spirit and
principles of the disclosure. All such modifications and variations are
intended to be
included herein within the scope of this disclosure and protected by the
following
claims.
lo
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