Note: Descriptions are shown in the official language in which they were submitted.
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BATTERY PACKAGING
BACKGROUND OF THE INVENTTON
1. Field of the Invention
The invention relates to batteries, such as, lithium ion
batteries, and to processes of preparing the batteries, such as,
lithium ion and lithium polymer and lithium metal batteries. The
invention also relates to battery packaging for batteries, such
as, lithium ion batteries, and to processes of preparing such
battery packaging for batteries, such as, lithium ion and lithium
polymer and lithium metal batteries.
2. Discussion of The Problems
Currently, lithium ion batteries are packaged in a hard
aluminum shell, which is impact formed or formed via deep-
drawing. Such hard shells are laser-welded to keep the liquid
electrolyte within the container, and to prevent the chemical
content of the shell from being exposed to moisture, and other
gases which impact the battery performance negatively. These
casings are expensive to make, available from a very limited
number of companies and also, more importantly, the shape and
form factors available are very limited. For instance, the
thickness of the case is not available in less than six (6)
millimeters.
The exorbitant cost and the limitation in sizes, shape and
thickness has driven the battery developers to a new approach to
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protect and contain such lithium ion and lithium polymer
batteries. The use of flexible aluminum-plastic laminates has
been introduced. Their low cost, the intended forming ability of
such laminates to provide deep cavities, the wide availability
and their high protection to moisture and gases have made such
materials understandably attractive as a concept. Also, the ease
of varying the size, i.e., length, width and thickness, of such
shapes provides the strongest argument for the choice of such
materials for such applications. The current metal shell
enclosure for batteries is also heavy and thick, when compared to
the invention herein. Such properties, weight and thickness are
key to new battery designs which need to be accommodated into
ever smaller appliances, such as, cell-phone, lap-top computers,
palm-top computers, notebook computers, cameras, etc. More and
more, weight and size is what determines the end-customer
preference for one or the other appliance. Furthermore, the
battery performance itself is another determining factor for the
sale of such products.
Over the last couple of years, the inventors herein and
others have designed and provided early versions of new laminates
for this application. These laminates were designed either for
cold-forming purposes, such as, a formed rectangular, straight
wall shaped cavity to house the battery bi-cells or as a pouch
type, thinner structure for typical three-sided or fin-seal type
pouches, the shape of which is well known to people skilled in
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the art of packaging. All of these materials had a number of
features in common:
They all contain an aluminum foil as the barrier material against
gases, such as, moisture and oxygen, to light, and to prevent the
liquid electrolyte from the battery to evaporate over time.
Beyond that, small variations were encountered from the type
first made available commercially by Alusuisse Flexible Packaging
in 1992. The latter is composed as:
Formable Non-formable
oPA, 25um Outside PET, l2um
Adhesive Adhesive
Aluminum foil, Aluminum foil,
45 to 60 um 10 to 60 um.
Tie layer Tie layer
PET or oPA, PET, 12 um
12 to 25 um
Tie layer Tie layer
Sealant, 50 um Inside Sealant, 50 um
Over time and in parallel with the development of the
battery technology itself, the tie layers, thickness of sealant
and foil were altered in some limited ways, and the sealant
chemistry and tie layers were improved over time. Typically, the
choice of sealant was made depending upon the chemistry of the
battery and its electrolyte and the process used for
manufacturing between acrylic acid modified polyethylene and
polypropylene. The tie layers were, therefore, also chosen
depending upon the above-mentioned sealant, and electrolyte, and
type of packaging used between epoxy-urethane or aliphatic
polyester type adhesives, and extended tie layers of acrylic acid
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modified polyethylene and malefic anhydride modified
polypropylene.
The thickness of the sealant and the presence of an
intermediate film on the inside of the structure, such as, a PET
(polyethylene terephthalate) or an oPA (oriented polyamide) film
are designed for the relevant connector thickness. The
connectors are metal strips made out of nickel, copper, aluminum
or stainless steel. The connectors are sealed between the two
sides of the package (such as, the top and the bottom for formed
cavities, or the front and back for pouch-type packages). The
connectors, also termed tabs, connect the anode and the cathode
from the battery to the exterior, as the positive and negative
poles, respectively.
The tab area constitutes the most complex part of the
battery shell. As with the current aluminum hard shell, the
aluminum-plastic laminate has to provide a very tight seal around
the tabs to prevent the electrolyte from migrating out of the
shell. At the same time, ingress of moisture along the same tabs
must be prevented.
The intermediate plastic films, such as, the oPA"film or the
PET film, are imbedded to assure that when sealed, the sealant
material is not squeezed in the tab area to the point where the
tabs come in contact with the aluminum foil from the package. At
which point, the battery would be shorted electrically. The oPA
or PET films are not compressible at the temperatures used to
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seal PP and PE, and, therefore, prevent the tabs from touching
the foil. (PP is polypropylene and PE is polyethylene.) The
sealant film or extrusion is designed in gauge to seal tabs in
various thickness range, but, mostly, the tabs have a thickness
between 50 and 80 microns, and, therefore, result in a tight,
very thick seal. The sealant then also has to be very thick,
which has some distinct disadvantages, as is shown below.
Therefore, materials of the state of the art are thick
because of the inside heat and pressure resistant film, such as,
the PET or oPA film, as well as the sealant material which is
either .polypropylene or polyethylene copolymer. The object of
new battery designs is to minimize size and weight of such
batteries. In order to maximize the volume for the battery bi-
cells in the case of formed cavities, the formed walls are as
straight as possible. The laminates used as the shell to protect
the bi-cells, and contain the electrolyte, are expected to be as
thin as possible. The materials of the current art are quite
thick and, therefore, are bulky, heavy and take a lot of valuable
space.
In order to reduce the size of the sealed and finished
battery, the seals are typically folded down in the case of a
formed bottom or folded along the body of the pouch. Such folded
seals with the state of the art materials take a significant
amount of space and volume, due to the thick nature of the
packaging material. The volume left for the battery is very
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significantly reduced because of the size of the folded seals. .
The amount of electrolyte that is absorbed by the sealant
material, either polypropylene or polyethylene, grafted or
copolymerized, is significant and allows the electrolyte to
evaporate over time. Typical electrolytes contain strong organic
solvents, such as, alkyl carbonates, for example, ethyl
carbonate, dimethylcarbonate, ethylmethyl carbonate, etc. These
strong solvents are soluble in the layers of the state of the art
laminates. Therefore, over time, the electrolyte found in
solution in the sealant, the PET and oPA films and tie layers
reduce the bond strength to some extent, but more importantly,
such electrolyte will also evaporate slowly at the edge of the
seal and the battery will dry out. Such batteries are exposed to
temperatures as high as 120°C for short periods of time,
temperatures such as 85°C for long term testing, and also cycling
between 60°C and 95°C over a long period of time.
Typically, when tested at 60°C over extended periods of
time, the electrolyte loss can be quite significant with the
state of the art package. Also, some of the laminated materials
of the current art lack forming capability and tend to crack at
the corners of the formed cavity. The formed cavity requires
almost straight wall angles (typically 4 degrees or less), which
is a tremendous stress for the material. Most of the time, the
lack of forming performance is associated with either the wrong
choice of aluminum alloy or the wrong type of PET or polyamide
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film. Once the aluminum foil is cracked by the forming process,
the barrier protection of the battery, such as to prevent the
electrolyte to evaporate, or moisture to ingress into the
package, is compromised.
The major drawback with the state of the art packaging
laminate, as described earlier, is that the tab area is extremely
difficult to seal tightly with such laminates. Such poor seals
lead to electrolyte leaking batteries and potential for corrosion
of the battery and tabs due to moisture ingress. At any rate,
the life and performance of the battery is compromised. Such
difficulty comes from the need for the sealant material to be
pressed during the heat seal process from its flat and homogenous
finish along the edge oz the tabs. During the heat seal process,
the sealant must flow to "caulk" the edges of the tabs. By doing
so, one takes the risk of pressing too much or too little of the
sealant material alongside of the tabs. In either case, the seal
will be weak and lead to leakage and migration which destroys the
battery performance. The sealant material is not available in a
variable quantity in the tab area as it is a web or extrusion as
an integral part of the laminate. Therefore, various"thickness
or sizes of tabs can only be accommodated by changing the sealant
layer thickness. The drawback of this approach is that the
sealant is then present in heavy gauge also everywhere else along
the battery seals. In these areas, the sealant is not desired in
such quantities, because it contributes to the moisture and
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electrolyte migration. Along the seals of the battery which do
not contain the tabs, the sealant should ideally be kept as thin
as possible and as moisture and electrolyte tight as possible.
The heat resistant films provided on the inside of the structure
are intended to prevent the tabs during the heat seal process
from touching the aluminum foil from the package. However, these
films also contribute to the migration of electrolyte and of
moisture, because neither of them are good barrier materials to
either moisture or electrolyte. PET and oPA are not considered
by a person skilled in the art to be high barrier materials to
water vapor or electrolyte. This invention demonstrates that
these materials can be eliminated while improving the barrier and
tab seal performance.
It is also now clear that every tab size and thickness more
or less would require a different laminated material to be
adapted to a more or less perfect seal of the tabs. This is a
very costly app roach, as often as the volumes associated with
certain battery or tab sizes are small, and, therefore, little or
no economy of scale is possible.
BROAD DESCRIPTION OF THE INVENTION
An object of the invention is to provide batteries, such as,
lithium ion batteries or lithium polymer batteries, and battery
packaging which have improved sealing of the connectors and
improved barrier performance to water vapor intrusion and
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electrolyte migration. Another object of the invention is to
provide batteries, such as, lithium ion batteries, and battery
packaging which have thinner laminates, and side seals that are
easier to fold, than the prior art batteries. Another object of
the invention is to provide batteries, such as, lithium ion
batteries, and battery packaging which have improved thermal
resistance to high temperatures, and therefore a safer product.
A further object of the invention is to provide batteries, such
as, lithium ion batteries, and battery packaging which have the
improved properties of the invention with connectors of various
sizes. Anotr~er object of the invention is to provide batteries,
such as, lithium ion batteries, and battery packaging which are
smaller in size and less in weight than those of the prior art.
A still further object of the invention is to provide laminates
for batteries, such as, lithium ion batteries, and battery
packaging which do not delaminate over time. Another object of
the invention is to provide processes for preparing the invention
batteries, such as, lithium ion batteries, and invention
packages.
The objects of the invention are achieved by the'invention
batteries, such as, lithium ion batteries, invention battery
packaging, and invention process of preparing them. Other
advantages and objections of the invention are set forth herein
or are obvious therefrom to a person skilled in the art.
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The invention involves improved batteries, particularly
improved lithium ion and lithium polymer batteries, and improved
battery packaging for batteries, particularly lithium ion and
lithium polymer batteries. The present thickness of lithium ion
batteries is about 6%~ mm or more. The new packaging allows for
thinner materials, so the invention batteries can be as thin as a
credit card.
More specifically, the invention involves a rechargeable
battery which includes a first laminate layer having a perimeter
region and a central region, and a second laminate layer having a
perimeter region and a central region. The first and second
laminate layers each comprise a metal foil, an outer polymer
layer bonded to one side of the metal foil, and a hot melt
polymer coating on the other side of the metal foil in at least
perimeter region of the metal foil. The metal foil is preferably
aluminum foil. The hot melt polymer coatings in the perimeter
regions of the first and second laminate are sealed together. A
central chamber is formed by the central regions of the first and
second laminate layers. There is an anode, a cathode and an
electrolyte arranged in an electrical current producing and
conducting manner in the central chamber. Two electrically
conductive connector strips are positioned between the two
perimeter regions. The connectors are typically aluminum, copper
or nickel. One 'end of one of the connectors is connected to the
anode, and one end of the other connector is connected to the
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cathode. Each other end of the two connectors extends beyond the
perimeter regions of the laminates. The hot melt polymer forms
very tight seals around the tabs which essentially prevent
electrolyte leakage and moisture incursion.
The hot melt polymer has significantly different physical
properties from the sealant polymer, even when the two are the
same or similar chemicals (polymers), which contributes to the
invention and its advantages. The hot-melt shows a low viscosity
compared to the sealant material at its melting temperature.
More specifically, the invention also involves battery
packaging which includes a first laminate layer having a
perimeter region and a central region, and a second laminate
layer having a perimeter region and a central region. The first
and second laminate layers each comprises a metal foil, an outer
polymer layer bonded to one side of the metal foil, and a hot
melt polymer coating on the other side of the metal foil in at
least perimeter region of the metal foil. The metal foil is
preferably aluminum foil. The hot melt polymer coatings in the
perimeter regions of the first and second laminate are sealed
together. A central chamber is formed by the central'regions of
the first and second laminate layers. Two electrically
conductive connector strips are positioned between the two
perimeter regions. The connectors are typically aluminum,
copper, or nickel. One end of one of the connectors is adapted
for connection to the anode in the central chamber. One end of
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the other connector is adapted for connection to the cathode.
Each other end of the two connectors extends beyond the perimeter
regions of the laminates. The hot melt polymer forms very tight
seals around the tabs which essentially prevent electrolyte
leakage and moisture incursion.
The purpose of the invention is not only to remedy the
problems of thickness of the packaging laminate and the problem
of tightly sealed tabs to prevent leakage and damage to the
battery, but also to provide a more robust material for the
forming process, and to reduce the electrolyte loss through the
seals. In the case where no forming process is reauired or
desired, a thinner and less expensive laminate can be used. In
both cases, the hot melt concept is used to provide tight seals
around the tabs. The materials of this invention also provide a
significantly higher thermal resistance to the high temperature
exposure that batteries can experience, and therefore creates a
safer product.
The invention allows for a maximized flexibility in sealing
various tab sizes and thickness by varying the amount and
location of hot melt material. The remainder of the package
still accommodates a seal with minimal sealant material to
minimize moisture and electrolyte migration. The amount of hot
melt must, however, be kept to a minimum in order to minimize
thickness, size and cost but more importantly to minimize
migration of electrolytes and water. The hot melt is designed
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for maximized resistance to the electrolyte and also for a
minimal absorption or solubility of the electrolyte. The hot
melt is also chosen from materials with high moisture barrier
performance, and low moisture solubility. The hot melt is made
out of the same family of resin as the sealant material of the
laminate in order to provide a strong weld with the package, when
the tabs and the hot melt are sealed together.
The hot melt can be applied at various locations and
sequences of the battery assembly. It can also be applied on the
tabs of the battery themselves prior or after the introduction of
the battery in the package. The hot melt can also be applied
directly onto the packaging material, for instance after forming,
if the package is a formed cavity, or after folding, if the
package is a pouch type.
The hot melt application itself is carried out with a gear
pump unit from a heated tank containing the not-melt, and
dispensed through nozzles at the desired location. The hot-melt
application principle is well known to people skilled in the art
of packaging. "
The hot melt material is designed, as mentioned above, from
the same family of organic polymers as that from which the
sealant in laminate is composed, so that the melting points of
both materials are close together. This allows, among other
things, the hot melt to be applied either on the packaging
material or on the battery tabs and cooled down to the solid
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state. When reaching the final assembly of the battery in the
package and such package is heat sealed, the side seals without
tabs are sealed under conventional heat, pressure and time. The
part of the package with the tabs protruding through the seal
(periphery regions) of the package, where the hot melt has been
applied is also sealed by the same process of heat, pressure and
time. The hot melt is reactivated by the heat and pressure and
bonds with. the packaging material and the tabs and, when made
molten by the heat and pressure, caulks the sides of the tabs so
that the seal is perfectly tight. The similar nature of the
package sealant and the hot melt allows for heat sealing with the
same parameters of heat, pressure and time as for the side seals.
When the sealing jaws are opened, the material is allowed to cool
down, and both the sealant material and hot melt sclidify into
very strong seals. These seals are mechanically strong so as to
resist the mechanical and thermal stresses of the life cycle of
the battery.
As used herein, the term electrolyte (or electrolytic
conductor) means a conducting medium in which the flow of current
is accompanied by the movement of matter in the form of ions.
The conducting medium is a liquid or a paste.
Lithium ion batteries use a liquid (nonaqueous) electrolyte.
The negative electrode is usually graphite or other carbon
material which is able to intercalate lithium ions. The positive
electrodes are lithium compounds or alloys, such as, LiCoO~.
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Lithium polymer batteries use a paste electrolyte which is
usually a mixture of oxides including at least one oxide.
The invention deals with primary batteries and particularly
with secondary batteries such as lithium polymer batteries and
preferably lithium ion batteries. The lithium ion and polymer
batteries are rechargeable.
The invention involves a lithium battery including a first
laminate layer having a perimeter region and a central region,
and a second laminate layer having a perimeter region and a
central region. The first and second laminate layers each
comprises a metal foil, an outer polymer layer bonded to one side
of the metal foil, and an inner polymeric sealant layer on the
other side of the metal foil. The inner polymeric sealant layers
of the perimeter regions of the first and second laminates are
sealed together. A central chamber is formed by the central
regions of the first and second laminate layers. There is an
anode, a cathode which is a-lithium compound or alloy, and
electrolyte arranged in an electrical current producing and
conducting manner in the central chamber. Two electrically
conductive connector strips are positioned between the two
perimeter regions. One end of one of the connectors is connected
to the anode, and one end of the other connector is connected to
the cathode. Each other end of the two connectors extends beyond
the perimeter regions. A hot melt polymer is located in a
sealing manner between each of the connectors and the perimeter
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regions of the sealant layers in the area of and around each of
the connectors. The hot melt polymer forms very tight seals
around the tabs which essentially prevent electrolyte leakage and
moisture incursion.
The metal foil is, for example, aluminum foil, soft annealed
aluminum alloy foil (preferred), copper foil, soft annealed
copper alloy foil or nickel. The lithium battery can be a
lithium polymer battery, with the metal foil as an aluminum foil.
The lithium battery can be a lithium ion battery. The metal foil
can be an aluminum foil having a thickness of 5 to 100 um. The
aluminum foil can be soft annealed aluminum foil.
The inner polymeric sealant layer can be a malefic anhydride
grafted polypropylene, an epoxy-propylene material or system,
propylene, an acrylic acid modified propylene, polyethylene, a
polyamide, a polyester or a urethane. The inner polymeric
sealant layer can have a thickness of 5 to 100 um. The inner
polymeric sealant layer can have a melting point of at least
90°C, preferably of at least 120°C.
The hot melt polymer can be a malefic anhydride grafted
propylene, an epoxy-propylene or system, propylene, ari acrylic
acid modified propylene, polyethylene, a polyamide, a polyester
or a urethane, which has been hot melt applied. The hot melt
polymer can have a melting point of at least 90°C, preferably of
at least 120°C, and which is similar to the melting point of the
inner polymeric sealant layer. The hot melt polymer can be a
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coating'over the entire surface of each of the inner polymeric
sealant layers.
The outer polymeric layer can be a polyester or a polyamide
or polypropylene. The outer polymeric layer can have a thickness
of 8 to 50 Vim. The outer polymeric layer can be a biaxially
oriented polyamide, a biaxially oriented polyester or biaxially
oriented polypropylene. The outer polymeric layer can be bonded
to the metal foil by means of an adhesive layer or a tie layer.
The adhesive layer can be a solvent based or solvent free
urethane based adhesive or~polyester based adhesive or epoxy-
based one or two component adhesive. The tie layer can be
polyethylene, or acrylic acid modified polyethylene or
polypropylene.
The lithium battery can have a pouch shape, or have a
rectangular (prismatic) straight wall shaped cavity, or be of the
three-sided or fin-seal type pouch.
The invention involves a lithium battery packaging including
a first laminate layer having a perimeter region and a central
region, and a second laminate layer having a perimeter region and
a central region. The first and second laminate layer's each
comprises an aluminum foil, an outer polymer layer bonded to one
side of the aluminum foil, and an inner polymeric sealant layer
on the other side of the aluminum foil. The inner polymeric
sealant layers of the perimeter regions of the first and second
laminates are sealed together. A central chamber is formed by
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the central regions of the first and second laminate layers. Two
electrically conductive connector strips are positioned between
the two perimeter regions. One end of one of the connectors is
adapted for connection to an anode in the central chamber, and
one end of the other connector is adapted for connection to a
cathode in the central chamber. Each other end of the two
connectors extends beyond the perimeter regions. A hot melt
polymer is located in a sealing manner between each of the
connectors and the perimeter regions of the sealant layers in the
area of and around each of the connectors. The hot melt polymer
forms very tight seals around the tabs which essentially prevent
electrolyte leakage and moisture incursion.
The invention involves a lithium ion battery including a
first laminate layer having a perimeter region and a central
region, and a second laminate layer having a perimeter region and
a central region. The first and second laminate layers each
comprises an aluminum foil, an outer polymer layer bonded to one
side of the aluminum foil, and a hot melt polymer coating on the
other side of the aluminum foil in at least perimeter region of
the aluminum foil. The hot melt polymer coating in the perimeter
regions of the first and second laminates are sealed together. A
central chamber is formed by the central regions of the first and
second laminate layers. There is an anode, a cathode which is a
lithium compound or alloy, and electrolyte arranged in an
electrical current producing and conducting manner in the central
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chamber. Two electrically conductive connector strips are
positioned between the two perimeter regions. One end of one of
the connectors is connected to the anode, and one end of the
other connector is connected to the cathode. Each other end of
the two connectors extends beyond the perimeter regions of the
laminates. The hot melt polymer forms very tight seals around
the tabs which essentially prevent electrolyte leakage and
moisture incursion.
The lithium battery is, for example, a lithium polymer
battery or a lithium ion battery. The metal foil can be aluminum
foil having a thickness of 5 to 100 um. The aluminum foil can be
soft annealed aluminum foil.
The inner polymeric sealant layer is a malefic anhydride
grafted polypropylene, an epoxy-propylene material or system,
propylene, an acrylic acid modified propylene, polyethylene, a
polyamide, a polyester or a urethane. The inner polymeric
sealant layer can have a thickness of 5 to 100 um and can have a
melting point of at least 90°C, preferably of at least 120°C.
The hot melt polymer can be a malefic anhydride grafted
propylene, an epoxy-propylene or system, propylene, an acrylic
acid modified propylene, polyethylene, a polyamide, a polyester
or a urethane which has been hot melt applied. The hot melt
polymer can have a melting point of at least 90°C, preferably of
at least 120°, and which is similar to the melting point of the
inner polymeric sealant layer.
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The outer polymeric layer can be a polyester or a polyamide.
The outer polymeric layer can have a thickness of 8 to 50 um.
The outer polymeric layer can be bonded to the metal foil by
means of an adhesive layer or a tie layer. The adhesive layer
can be a solvent based or solvent free urethane based adhesive or
polyester based adhesive or epoxy-based one or two component
adhesive. The tie layer can be polyethylene, or acrylic acid
modified polyethylene.
The lithium battery can have a pouch shape, or have a
rectangular straight wall shaped cavity, or be of the three-sided
or fin-seal type pouch.
The invention further involves a lithium battery packaging
which includes a first laminate layer having a perimeter region
and a central region, and a second laminate layer having a
perimeter region and a central region. The first and second
laminate layers each comprises an aluminum foil, an outer polymer
layer bonded to one side of the aluminum foil, and a hot melt
polymer coating on the other side of the aluminum foil in at
least perimeter region of. the aluminum foil. The hot melt
polymer coatings in the perimeter regions of the first and second
laminates are sealed together. A central chamber is formed by
the central regions of the first and second laminate layers. Two
electrically conductive connector strips are positioned between
the two perimeter regions_ One end of one of the connectors is
adapted for connection to an anode in the central chamber, and
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one end of the other connector is adapted for connection to a
cathode in the central chamber. Each other end of the two
connectors extends beyond the perimeter regions of the laminates.
The hot melt polymer forms Very tight seals around the tabs which
essentially prevent electrolyte leakage and moisture incursion.
If the inner surfaces of the metal foils of the laminates
are not completely covered by sealant coating or hot melt polymer
coating, the metal foil in the laminates in the seal area should
be nonconductive or the edges sealed of the laminates should be
covered with a non-electrically conductive polymer or other
material so as not to cause electrical shorting of the batteries.
The lithium ion and lithium polymer batteries of the
invention are very small (thin and ultra thin) and can be used in
cell-phones, lap-top computers, cameras, palm top computers,
notebook computers, electric shavers, cordless phones, pagers,
beepers, calling cards, garage door openers, baby monitors,
wireless microphones, portable electronic products and the like.
The batteries of the invention include other batteries which use
alternative chemical systems. The batteries of the invention can
include solid state lithium batters (i.e., no liquid c5r paste
electrolyte).
The outer polymer layer of the invention laminates is
generally a polyamide, polyester or polypropylene film/layer.
The outer polymer layers of the laminates can be, for
example, a polyamide-based thermoplastic comprised mainly of
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polyamide-based thermoplastics. Belonging to the polyamide-based
thermoplastics are, for example, the polyamides polyamide 6, a
homopolymer of E-caprolactam (polycaprolactam); polyamide 11,
polyamide 12, a homopolymer of c~-laurinlactam
(polylaurinlactam); polyamide 6.6, a homo-poly-condensate of
hexamethylene-adiamine and adipinic acid (poly-hexamethylene-
adipamide); polyamide 6.10, a homo-poly-condensate of
hexamethylene-diamine and sebacinic acid (poly-hexamethylene-
sebacamide); polyamide 6.12, a homo-poly-condensate of
hexamethylene-diamine and dodecandic acid (poly-hexamethylene-
dodecanamide) or polyamide 6-3-T, a homo-poly-condensate of
trimethyl-hexamethylene-diainine and terephthalic acid (poly-
trimethyl-hexamethylene-terephthalamide), and mixtures therefrom.
Preferred are polycaprolactams.
The outer polyamide layers can include, e.g., monofilms or
monolayers and composites of two or more films or layers of
polyamides, polyamide mixtures or mixed, block, grafted or
copolyamides.
The outer polyamide layers can be present as monofilms,
however, also as composites of two or more films.
The outer polyamide layers or films contain additives, such
as, stabilizers, softeners, filler materials, pigments, etc.
The outer polyamide layers can be stretched and are usefully
uniaxially, preferably biaxially stretched. The outer polyamide
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layers can contain or be stretched polyamide-based
thermoplastics. Very strongly preferred are uniaxially or in
particular biaxially stretched polyamide films.
The flow behavior of the outer polyamide layer in the form
of films and in particular in the form of biaxially stretched
polyamide films is usefully as isotropic as possible.
Furthermore, the outer polyamide films that are preferred
are those with a flow behavior that results in a high degree of
strain hardening. The high degree of strain hardening is
evidence of increasing stress in the film in the longitudinal and
transverse directions with increasing elongation.
Particularly suitable polyester, polyamide or polypropylene
layers have a high R value, an R value lying in particular above
1. The R value expresses whether the material yields preferably
from the width or from the thickness of the particular film. An
R value above 1 denotes that the material yields preferably from
the width of the sample.
The preferred films include, for example, biaxially oriented
polypropylene and particularly preferred polyamide or polyester
films having a tensile strength in both directions of:.more than
150 MPa, preferably more than 200 MPa.
The extension to break of preferred films is, for example,
above 40 percent and in particular above 50 percent. The tension
in the extension region of 5 to 15 percent in preferred films is
advantageously between 40 and 120 MPa and in particular between
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50 and 100 MPa.
The metal foil or layer of the formable laminate of the
invention can be, for example, iron, steel or copper. A
preferred metal foil is aluminum or an aluminum alloy. A metal
layer is advantageously aluminum having a purity of 98.6 percent
and higher, preferably 99.2 percent and higher, and particularly
preferably 99.5 percent and higher. Aluminum alloys, for
example, of the type AA8079 or AA8101 or AA8021, are also
advantageous.
A soft-annealed, fine-grain and/or largely texture-free
(isotropic) aluminum thin tape, i.e., a continuous metal layer
that has no perforations, cuts or discontinuities, in particular
having at least 5 and particularly preferably 7 grain layers over
the thickness of the tape, is particularly preferred as a metal
layer.
The surface of the metal layer and in particular the
aluminum layer is preferably homogeneous, without residual
greases and having a defined surface. The aluminum surfaces can ,
be treated, for example, with stoning lacquers based on epoxide
or phenol, or with conversion layers, such as mixed oxide and/or
hydrate layers. Furthermore, the surfaces can be pretreated by
means of a corona discharge treatment.
The laminating adhesive is advantageously used to join the
outer polymer film/layer to the aluminum foil. The laminating
adhesive can be applied to the surface to be adhered by lacquer
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laminating.
Examples of suitable adhesives are vinyl chloride
copolymers, vinyl chloride-vinyl acetate copolymers,
polymerizable polyesters, vinylpyridine polymers, vinylpyridine
polymers in combination with epoxy resins, butadiene-
acrylonitrile-methacrylic acid copolymers, phenol resins, rubber
derivatives, acrylic resins, acrylic resins with phenol or epoxy
resins or acrylate copolymers, or organosilicon compound, such as
organosilanes.
The organosilanes are preferred. Examples of these are
alkytrialkoxysilanes having an amino functional group,
alkyltrialkoxysilanes having an epoxy functional. group,
alkyltrialkoxysilanes having an ester functional group,
alkyltrialkoxysilanes having an aliphatic functional group,
alkyltrialkoxysilanes having a glycidoxy functional group,
alkyltrialkoxysilanes having a methacryloxy functional group, and
mixtures thereof. Examples ,of those organosilanes are Y-
aminopropyltriethoxysilane and N-~i-(aminoethyl)-Y-
aminopropyltrimethoxysilane, Y-(3,4-epoxycyclohexyl)-
ethyltrimethoxysilane, Y-glycidoxypropyltrimethoxysilane, and Y-
methacryloxypropyltrimethoxysilane. These compounds are known
per se in the specialist field.
Further suitable adhesion promoters are adhesives, such as
for example nitrite rubber-phenol resins, epoxides,
acrylonitrile-butadiene rubber, urethane-modified acrylics,
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polyester co-polyamides, hot-melt polyesters, polyisocyanates
cross-linked with hot-melt polyesters, polyisobutylene-modified
styrene-butadiene rubbers, polyurethanes, ethylene-acrylic acid
mixed polymers and ethylene-vinyl acetate mixed polymers.
The polyurethanes are particularly preferred. Depending on
the type, the adhesives may be used with or without solvents or
from aqueous solution.
As a rule the adhesive layer thickness is kept from 1 to
12 um and preferably 1.5 to 9 u.m. Instead of the layer
thickness, the amount of adhesive, especially between the metal
foil and the outer polymer film arranged right next to the side
of the metal .layer, can be expressed by the amount of laminating
adhesive. The amount is, for example 1.0 to 14 g/m=,
advantageously 1.5 to 9 g/mz, and preferably 1.5 to 6 g/mz. The
amount is given without miscellaneous solvent. The outer polymer
films may be heat-laminated on the aluminum surface.
The polypropylene sealant is a base polyolefin material,
such as, atactic or isotactic polypropylene. In order to promote
adhesion to metal, grafting of functional groups to the base
polyolefin material is performed. Malefic anhydride grafting of
polypropylene is a typical type modification to promote metal ,
adhesion.
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BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Figure 1 is a top view of the formed version of a prior art
lithium ion battery;
Figure 2 is a lateral cross-sectional view along line 2-2
in Figure 1;
Figure 3 is a longitudinal cross-sectional view along line
3-3 in Figure 1;
Figure 4 is a cross-sectional view of the formed version of
the tab region of the prior art battery of Figure 1;
Figure 5 is a top view of the invention lithium ion battery;
Figure 6 is a lateral cross-sectional view along line 6-6
in Figure 5;
Figure 7 is a longitudinal cross-sectional view along line
7-7 in Figure 5;
Figure 8 is a longitudinal cross-sectional view of the tab
region of the invention battery of Figure 5;
Figure 9 is another longitudinal cross-sectional view of the
tab region of the prior art battery for comparison with Figure
10;
Figure 10 is another longitudinal cross-sectional view of
the tab region of the invention battery for comparison with
Figure 9;
Figure 11 is a perspective view of the fin-seal type of the
pouch version of the invention lithium ion battery;
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Figure 12 is a lateral cross-sectional view along line
12-Z2 of the central chamber region in Figure 11;
Figure 13 is a partial perspective view of the non-tab end
of the invention battery of Figure 11;
Figure 14 is an end view of the invention battery of Figure
11; .
Figure 15 is a partial perspective view of the tab end of
the invention battery of Figure 11;
Figure 16 is a lateral cross-sectional view along line
16-16 of the tab region of the invention battery of Figure 11;
Figure 17 is a top view of the pouch version of the
invention lithium ion battery;
Figure 18 is a side view of the invention battery of Figure
17; and
Figure 19 is a front view of the invention battery of Figure
17.
DETAILED DESCRIPTION OF THE INVENTION
The materials described here, in combination with the use of
the hot melt to seal the tabs, provide an improved and novel
package for lithium-based batteries. The invention provides a
lighter package which prevents leakage of the electrolyte and
impermeability to moisture particularly, and to some extent
oxygen (true for the laminate and the hot melt). The critical
sealing of the tabs and the making of a tight seal at that
location is what the invention helps to improve with a novel
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approach.
Tabs of various thickness and sizes can easily be
accommodated, without changing any of the materials, by simply
controlling the amount and placement of the hot melt.
Other benefits of the invention are thinner materials, which
also are lighter and, therefore, minimize the weight and size of
the battery. These materials also provide seals that are easier
than the state of the art materials to bend into small radii in
order to also minimize the overall battery size.
Sealant materials and hot melt materials can be, for
example,
- Malefi c anhydride grafted polypropylene (a preferred
polymer)
- Epoxy-polypropylene systems
- Polypropylene
- Acrylic acid modified polyethylene (also known as EAA)
- Polyethylene -.-
- Polyamide
- Polyester .
The thickness of the sealant can be from 5 to 100 um,
preferably from 5 to 50 um, and most preferred from 5 to 20 pm.
The choice of sealant concentrates on materials which have a
melt point (seal resistance) higher than the temperature to which
batteries are exposed, such as 120°C (for safety purposes), and
have resistance to the electrolyte, at high temperatures.
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The choice of hot melt polymer is also tied to a similar
chemistry and melt point as the sealant in order for the laminate
to allow for ease of sealing and caulking of the sides of the
tabs.
The sealant material and the hot melt are also chosen to
minimize electrolyte loss and moisture migration, both of which
are detrimental to battery performance. Therefore, thin sealants
and minimal amounts of hot melt are recommended to limit
migration.
Another important factor is that, when compared to the state
of the art (prior art) laminates, the invention provides a
package that can by no means delaminate over time between the
layers. The state of the art materials are sensitive to chemical
degradation over time, as well as creep, which tends to
delaminate part of the structure over time, and expose the
battery to migrations. The invention does not delaminate and
expose the battery to migration. In practice, this is a
tremendous advantage of the invention.
The hot melt can also be used advantageously with fin-seal
type pouches, certainly on the tab side, and also on the opposite
side, where the fin joins the end-seal, by caulking the material
overlap, which is typically a weak seal or one that is difficult
to perform on a pouching machine.
As far as the metal layer is concerned, there is a
difference depending upon whether or not the material has to be
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formable:
Formable
- aluminum alloy 98.6. percent pure or higher, soft annealed
- gauge from 10 to 100 um, preferably 20 to 70 um and most
preferably 25 to 60 um, (one reduction to practice was
45 um, but could readily also be 60 um)
- the metal could also be copper or copper alloys, soft
annealed, or nickel, for example.
Non-formable
- aluminum 98.6 percent or higher, soft annealed
- gauge from 5 to 100 um, preferably 10 to 50 um, and most
preferably 10 to 30 um, (one reduction to practice was
2 5 ~.tm)
- the metal could also be copper or copper alloys, soft
annealed, or nickel, for example.
For the outside layers:
For formable structures, the preferred material is biaxially
oriented polyamide 6 or 6.6, with a gauge from 10 to 200 ~,~m,
preferably 10 to 50 um, and most preferably 10 to 30~un (one
reduction to practice was 25 um biaxially oriented polyamide).
The use of other materials, such as, biaxially oriented polyester
and biaxially oriented polypropylene, in the same thickness
ranges can also be used.
The outside layers can be bonded to the metal via an adhesive
layer, which can be urethane based, or polyester based, or epoxy-
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based one or two component adhesives, solvent based or solvent
free. The outside layers could also be bonded to the metal with
an extruded tie layer made of polyethylene or modified
polyethylene, such as, acrylic-acid modified polyethylene.
For non-formable structures, the preferred material is a
biaxially oriented polyester film, or biaxially oriented
polyamide, or biaxially oriented polypropylene. The gauge
(thickness) can be from 10 to 100 ~.tm, preferably 10 to 50 alm, and
most preferably 10 to 30 ~zm, (one reduction to practice was 12 ~m
biaxially oriented polyester).
The laminates in the non-formable embodiment are very
flexible, more so than the formable embodiment.
Figures 1 to 4 show embodiments of prior art (state of the
art) lithium ion battery 100. Figure 1 shows a top view of
lithium ion battery 100 with two metal tabs 107 extending beyond
perimeter region 111, which surrounds central chamber 112.
Perimeter region 111 includes front seal area 113 and side and
back seal areas 109. Figure 2 is a lateral cross-sectional view
of lithium ion battery 100. Stacked bi-cells 108 are shown in
central chamber 112. The electrolyte is contained in; central
chamber 112. Side seal areas 109 are shown with bent over
portions 114, which in the actual battery assembly are completely
folded under. Figure 3 is a longitudinal cross-sectional view of
lithium ion battery 100. Aluminum tabs 107 extend completely
through front seal area 113 and connect with stacked bi-cells 108
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by means of aluminum flat leads 115. Central chamber 112 is
formed in bottom laminate 116 and is covered by top laminate 117.
Front seal area 113 and side and back seal areas 109. Referring
to Figure 4, top laminate 117, from the outside layer to the
inside layer, is composed of:
101 - Polyethylene terephthalate (PET) or oriented
polyamide (oPA) film .
102 - Urethane adhesive layer
103 - Aluminum foil
104 - Urethane or acrylic acid modified polyethylene
(EAA) layer
105 - Polyethylene terephthalate film
106 - Polypropylene (PP) or acrylic acid modified
polyethylene sealant layer.
Referring to Figure 4, bottom laminate 7.16, from the inside layer
to the outside layer, is composed of:
106 - Polypropylene or acrylic acid modified
polyethylene sealant layer
105 - Polyethylene sealant terephthalate film
104 - Urethane or acrylic acid modified polyethylene
layer
103 - Aluminum foil
102 - Urethane adhesive layer
101 - Polyethylene terephthalate or oriented polyamide
layer.
As seen in Figure 4, aluminum tabs) 107 lies between and is
bonded (tab seal 110) to inner sealant layers 106 of top laminate
117 and bottom laminate 1I6. The seals around tabs 10,7 are prone
to electrolyte leakage and moisture incursion.
Figure 5 to 8 show preferred embodiments of invention
lithium ion battery 118. Figure 5 show a top view of lithium ion
battery 118 with two metal tabs 107 extending beyond perimeter
region 1II, which surrounds central chamber 112. Perimeter
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region 111 includes front seal area 113 and side and back seal
areas 109. Figure 6 is a lateral cross-sectional view of lithium
ion battery 118. Stacked bi-cells 108 are shown in central
chamber 112 (which has a rectangular horizontal cross-section).
The electrolyte is contained in central chamber 112. Side seal
areas 109 are shown with bent over portions 114, which in the
actual battery assembly are completely folded under. Figure 7 is
a longitudinal cross-sectional view of lithium ion battery 118.
Aluminum tabs 107 extend completely through front seal area 113
and connect with stacked bi-cells 108 by means of aluminum flat
leads 115. Central chamber 212 is formed in bottom laminate 119
and is covered by top laminate 120. Front seal area 113 and side
and back seal areas 109. Referring to Figure 8, top laminate
120, from the outside layer to the inside layer, is composed of:
101 - Polyethylene terephthalate or oriented polyamide
film
102 - Urethane adhesive layer
103 - Aluminum foil__
111 - Polypropylene, polyamide or polyethylene
terephthalate hot melt coating.
Referring to Figure 8, bottom laminate 119, from the inside layer
to the outside layer, is composed of:
111 - Polypropylene, polyamide or polyethylene
terephthalate hot melt coating
103 - Aluminum foil
102 - Urethane adhesive layer
101 - Polyethylene terephthalate or oriented polyamide
film.
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As seen in Figure 8, aluminum tabs) 107 lies between and is
bonded (tab seal 110) to hot melt coatings 106 to laminate 120
and bottom laminate 119. The hot melt polymer 106 seals around
tabs 107 are very tight seals which essentially prevent
electrolyte leakage and moisture incursion.
A comparison of the sealing around the tabs 107 in prior art
lithium ion battery 100 and invention lithium ion battery 121 is
shown in Figures 9 and 10. Prior art lithium ion battery I00 in
Figure 9 is the same as in Figures 1 to 4.
Figure 10 is a cross-sectional view of embodiments of
invention lithium ion battery 121. Referring to Figure 10, top
laminate 123, from the outside layer to the inside layer, is
composed of: :.
101 - Polyethylene terephthalate or oriented polyamide
film
102 - Urethane adhesive layer
103 - Aluminum foil
106 - Acrylic acid modified polyethylene, or
polypropylene or malefic anhydride modified
propylene sealant layer
111 - Polypropylene, polyamide or polyethylene
terephthalate hot melt coating.
Referring to Figure 10, bottom laminate 122, from the; inside
layer to the outside layer, is composed of:
111 - Polypropylene, polyamide or polyethylene
terephthalate hot melt coating
106 - Acrylic acid modified polyethylene, or
polypropylene or malefic anhydride modified
propylene sealant layer
103 - Aluminum foil
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102 - Urethane adhesive layer
101, - Polyethylene terephthalate or oriented polyamide
film.
The hot melt polymer tab seal areas of invention battery 121
are much better than the tab seal areas of prior art battery 100.
Figure 11 to 16 shows a fin-seal type pouch embodiment of
invention lithium ion battery.124. Figure 11 is a perspective
view of the lithium ion battery 124 with pouch body 125 with fin-
seal portion 126. Two electrically conductive metal (preferably
aluminum) tabs 107 extend beyond front perimeter region 127 of
battery 124. See Figure 15, which sho~rJS the front end of battery
124. Figures 13 and 14 show the back end of battery 124. Body
125 and fin-seal portion 126 are composed of laminates used in
the invention. Battery 124 is composed of one piece of laminate,
with front tab seal 127, front fin-seal 128, back seal 129 and
back fin-seal 130. Hot melt polymer 131 is coated on the inside
surfaces of the laminate in the region of front tab seal 127 and
laminate in the region of front tab seal 127 and front seal fin-
seal 128. When front tab seal 127 and front fin-seal 128 are
formed, hot melt polymer 131 completely seals around tabs 107.
This is best shown in Figure 16. Hot melt polymer 13~ is also
coated on the inside of the laminate in the region of back seal
129 and back fin-seal 130. When back seal 129 and back fin-seal
130.,are formed, hot melt polymer 131 completely seals the back
region (hole or void) formed by the intersection of back seal 129
and back fin-seal 130. Figure 12 is a lateral cross-sectional
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view of battery 124. Stacked bi-cells 108 are shown in central
chamber 112. The electrolyte is contained in central chamber
112. The front and back seals are very tightly sealed by hot
melt polymer 131 to electrolyte leakage and moisture (water and
vapor) incursion.
Figure 17 to 19 show a three-sided seal (nonformable) pouch
embodiment of the invention. Figure 17 is a top view of the
lithium ion battery 132 with pouch body 133 with front tab seal
region 134 and side seal regions 135, and with central chamber
136. Two electrically conductive metal (preferably alum=num,
copper or nickel) tabs 107 extend beyond the front tab seal
region 134. As shown in Figure 18, body 133 of battery 132 is
formed by laminate 137 of the invention folded over on itself.
Hot melt polymer 140 is coated on the inside surfaces of folded
over laminate 137 in the region of front tab seal 134. When
front tab seal 134 is formed, hot melt polymer 140 completely
seals around tabs 107. This is best shown in Figure 19. Stacked
bi-cells (not shown) and electrolyte are contained in central
chamber 112. The front tab seal 134 is very tightly sealed by
hot melt polymer 140 to electrolyte leakage and moisture
incursion.
The state of the art seal strength, for instance, can be as
follows:
State of the Art: Invention:
6 to 15 N/l5mm >10 to 20 N/l5mm
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Therefore, typically, an increase in seal strength of 200 percent
has been achieved. The seal strength as a function of the
temperature of use is also of great importance. The seals must
not fail under thermal and mechanical stress. Therefore, the
choice of sealant material is very important. Besides its
chemical resistance, the sealant must also provide high thermo-
mechanical resistance. The choice of sealant in the invention
concentrates on materials that have a melt point above the
highest temperature to which the batteries are exposed. The
highest temperature to which batteries are exposed to from a
testing standpoint is 120°C, and, henceforth, the temperatures
listed above. Long term testing is often carried out at 60°C for
at least 30 days and 85°C for four (4) days. At such ,.
temperatures, the absence of leak and also a minimal electrolyte
loss via migration through the seals are important.
The sealants of choice, therefore, nave a melt point higher
than the maximum temperature to which batteries are exposed,
i.e., higher than 120°C. ,
One of the systems of choice involves a thin lacquer coating
on the laminate foil: "
Tnvention:
Polyamide or polyester film, 12 to 50 pm, preferably 12 to 30 ~.tm
Adhesive or tie layer
Aluminum foil, 6 to 100 um, preferably 20 to 60 um., most
preferred 20 to 50 um
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Polypropylene sealant, 3 to 50 um, preferably 3 to 30 um, most
preferred 3 to 10 um.
The invention material can be half as thick as the state of
the art materials, mostly because it avoids the bulky sealant
material in the laminate for the sealing of the tab area, and
also eliminates the heat resistant films, such as, PET or oPA.
EXAMPLE I
As a formable laminate structure of the invention:
Polyamide film, 25 um
Urethane adhesive
Aluminum foil, 45 um
Polypropylene coating, Gum
The invention could be formed into the same shapes as the state
of the art material, i.e., to a depth of 4.5 mm with almost
straight walls (4 degree angle, as with state of the art
materials).
The seal resistance to electrolyte at elevated temperature
was as follows, when formed, electrolyte filled and sealed
packages were exposed to 60°C for 30 days:
State of the Art: Invention:
22 to 105 mg, depending upon structure 1.8 to 3~0 mg
The above numbers express the amount of electrolyte that migrated
through seals over a 30-day period. Therefore, the invention is
at least seven (7) times tighter and more resistant to the
electrolyte than the state of the art materials.
The tab area is sealed with the help of a hot melt, which is
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also part of the invention. The hot melt compensates for the
thickness difference around the tabs that can typically be from
20 to 100 microns thick, depending upon the battery. Hot melt of
polyamide, polyester or polyolefin nature, preferably
polypropylene-based, is applied on the laminate of the invention
or on the tabs themselves to perfectly caulk the sides of such
tabs and provides a perfectly tight seal. At the same time, the
hot melt protects the tabs from coming in contact with the
aluminum foil from the package, thus avoiding electric shorting
of the battery.
The importance of the similar nature of the hot melt with
the sealant from the laminate is to facilitate the heat seal
process. The hot melt and the sealant from the laminate of the
invention are sealed together with the tabs and the remainder of
the perimeter regions are sealed at the same time, with the same
temperature, pressure and dwell time conditions.
The propylene sealant from the reduction to practice of the
invention has a melting point of 150°C, and the hot melt has a
melting point of 156°C, which allows a perfect match between the
two materials during the heat sealing process.
The tab area is very difficult to keep tight to electrolyte
migration over time using the state of the art material. As
shown above, the same parallel test was conducted with formed,
filled-with-electrolyte, sealed packages, this time both with
tabs in both the state of the art materials and in material from
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this invention with the hot melt. The tab material chosen was
aluminum, 50 micron thick. The sealed packages were exposed to
60°C for 20 days, and the electrolyte loss was quantified:
State of the art materials Invention with
with sealed tabs: sealed tabs:
111 to 736 mg loss depending 12 to 21 mg
upon structure
The above data shows the amount of electrolyte that was lost
through the seals, including the area of and around the sealed
tabs after the 20 day period. It is, therefore, apparent that
the material of the invention, together with the invention hot
melt concept for sealing the tabs is at least five (5) times
higher in performance than the state of the art system. The
invention can also provide further reduction of the amount of
electrolyte loss.
In addition to these remarkable performance improvements in
terms of battery protection, the laminate of the invention is
typically 25 percent lighter than the state of the art materials.
At the same time, the material of the invention is also typically
40 percent thinner than state of the art material for:,formable
structures.
Furthermore, different sizes and thickness of tabs can
easily be accommodated by varying the amount of hot melt that is
applied in order to caulk the sides of such tabs. This can be
done without having to modify the laminate of the invention. On
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the contrary, when using the state of the art materials, the
sealant layer needs to be varied in order to accommodate thicker
or thinner tabs. Therefore, if the tabs are 80 microns thick,
instead of 50 microns, the sealant material in the state of the
art laminates will almost have to be doubled in thickness.in
order to provide~a tight seal around the tabs. This will also
impact the overall migration of electrolyte and moisture through
the seal, because the thicker the seal, the larger the migration
path for the electrolyte and for moisture. In addition, the cost
of the structure goes up as well. Furthermore, the side seals
that need to be folded are also thicker and take more space,
while becoming more difficult to fold, because of the bulky
nature of the state of the art laminate.
The invention overcomes all these drawbacks with proper
dosage of hot melt in the tab seal area, without compromising any
of the side seals. Migration can always be kept at a minimum and
the folding of the side seals is not impacted at a11.
The seal area, which then needs to be folded, is comprised
of two layers of material of the invention or of state of the art
material. Therefore, the thickness of the seals is a~:so 40
percent thinner with the invention, which provides a tremendous
decrease in the space (volume) lost to the folded seals. In
addition, the material of the invention has a characteristically
improved deadfold performance compared to the state of the art
material. This makes the folding process tremendously easier,
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which is another advantage of the invention.
If forming is not desired, a thinner laminate on the basis
of the invention can be used:
Polyester or polyamide film, 9 to 12 um
Urethane adhesive _
Aluminum foil, 10 to 25 um
Polypropylene coating, 3 to 6 um
In order to ascertain that there is absolutely no pinholes
in the aluminum foil of the preferred embodiment, a minimum
thickness of foil of 20 to 25 microns is most preferred.
EXAMPLE 2
Laminates are used to prepare a non-formable lithium ion
battery. The laminates are composed of:
Polyester film, PET 12 um
Urethane adhesive
Aluminum foil, 25 um
Polypropylene coating, 3 um
The hot melt is also used to seal and caulk the metal tabs with
the laminate of the invention to provide a perfectly tight seal.
If a fin-sealed type pouch is made, it is known in the art,
that the two ends where the fin-seal joins the end seals is most
critical from an integrity standpoint. The invention also
applies a hot melt at the joint between the fin-seal and the end
seals, in addition to the tab areas.
