Note: Descriptions are shown in the official language in which they were submitted.
~08230S
This lnvent~on relates to electrical cells and
~atter~es, and part~cularl~ to a novel cell and batter~
construct~on especially suited to very high current drain
applications.
An automatic photographic system currently in
widespr~ad use comprises the Polaroid SX-70 Land Camera,
equipped to expose and process film units provided in
cassettes of ten. All power for ~his system is sup-
. .
plied by a thin, flat, disposable battery in each cas-
sette.
The requirements of a disposable battery suit-
able for use in an automatic photographic system such as
~ha Polaroid SX-70 Land system are onerous. In order to
operate the camera and eject and process the film units,
relatively high current drain capabilit~ as well as
adequate capacity are needed in a package that is both
highly compact and sufficiently inexpensive to justify
its disposal after the film units with which is is pack-
aged have been exposed and processed.
Still more ambitious goals have been proposed
for automatic photographic systems p~ered b~ compact,
disposable batteries. In United States Patent No.
3,846,812, issued on November 5, 1974 to Conrad H. Biber
for Automatic Electronic Flash Camera, the desirability
of obtaining the power for an electronic flash unit,
as ~ell as for the camera, from the battery in the
Polaroid SX-70 film pack is expressed, and circuits are
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3~)S
described for dividing the operating cycle of the camera in
such a way as to minimize the requirements on the battery.
Assuming a flash unit of relatively modest output for the
SX-70 format, and typical recharge times of ten to twenty
seconds~ it is thus possible to use the battery currently
sold in the SX-70 film pack even for this considerably more
demanding purpose. The ability to use a more powerful flash
unit, while obtaining shorter recharge times~ would obviously
be welcomed. However, the current production battery is not
capable of the greatly increased requirements of power and
current density that such an e~tension would imply.
It would obviously be a simple matter to increase
the capabilities of the system by considerably increasing
the size of the battery, or by using a plurality of batteries.
Neither expedient would be compatible with the concept of
a compact and self-contained system, in which the battery
makes negligible contrlbution to the size of the film pack,
being for the most part disposed in unused space under the
film ad~ance spring. ~ ~;
The current production battery is disposed on a
card about 3.5 by 4.2 inches, has external dimensions of
about 2.75 by 3.42 by .125 inches, and has an active electrode
area of about 4.7 square inches. It is possible to increase
the electrode area by about twenty five percent without
changing the external dimensions, effecting a significant
improvement in capacity and in internal impedance. The
capacity of the battery can also be increased by doubling the
weight of the cathodes, at the cost of about .025 inches in
thickness~ an amount that is within the limit that the film
pac~ will accept. In this manner, the capabilities of the
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3()S
battery can be increased sufficiently so that a forty watt
second flash unit could be used with the camera for a full
cycle of ten exposures. But the results would still leave
something to b~ desired, in the two central respects of
cos t and performance.
The battery currently sold with the SX-70 film pack
employs a so-called "dry patch" construction for both anodes
and cathodes. These are formed by depositing slurries of -
paxticulate material, comprising zinc powder and a little
carbon for the anode, and manganese dioxide with more carbon
for the cathode, in aqueous systems including di~persing
agents and binders. After deposition on the conductive plastic
substrates used as current collectors and intercell
connectors, these slurries are dried to form adherent patches.
D~ring the assembly of the battery, these dry patches are
coated with gel electrolyte, whereby the anodes and cathodes
are brought into electrochemical communication through
the separators. This process is undesirably complex. Moreover,
the binders used to hold the patches together contribute
significantly to the internal impedance of the battery. The
result is that when the cathode patches are increased in
thickness enough to provide the capacity to handle a forty -
watt second flash unit in the SX-70 system, recharge times
are undesirably long.
The objects of this invention are to increase the
current drain capabilities o~ thin, laminar batteries, without
a substantial increase in size, while simplifying the
manufacture and thereby increasing the yields and decreasing
th~ cost of such batteries.
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lOB2305
Briefly, the above and other objects of the
invention are attained by a novel battery construction in
~hich the cathodes are deposited, by extrusion, for example,
as slurries containing from about twenty three to about
thirty percent of water, and preferably from twenty six to
twenty eight percent of water, based on the weight of slurry.
Where optimum performance measured by short flash unit
recharge timas is the first objective, it is preferred to
make the anodes in conventional dry patch form. However,
whe~e manufacturing simplicity and cost are first in order
of priority, assuming that good flash charging capability
can also be achieved, it is preferred to make the anodes in the
form of slurries containing from twenty-five to forty percent,
and preferably about twenty-six to thirty-six percent, of
water based on the weight of anode slurry. In this manner,
the steps of drying and gel coating can be eliminated, and
the addition o-f high impedance binders can be avoided.
Surprisingly, the absence of adhesives and binding
agents in the slurries does not adversely affect the internal
impedance of the batteries, as indications in the literature
would lead one to expect, but quite the reverse. In
particular, U. 5. Patent No. 3,617,387, issued on November 2,
1971 to Carl Albert Grulke and Thomas Arthur Reilly for
Battery Construction Having cell Components Completely
Internally Bonded With Adhesive proclaims the necessity for
adhesive bonds in batteries for which no external-compressive
stress mechanism is provided. Also, in U. S. Patent No. `~
2,870,235, issued on January 20, 1959 to D. G. Soltis for
Cathodic Envelope Cell, where wet mixes for both cathode and ~-
anode are described without any mention of binders, the ~ -
.
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8~:305
elements are sealed in moistureproof envelopes ~nd are
pacXaged as to make possible the application and maintenance
of "very heavy end-wise pressure on a stack of cells"; e.g.,
about 136 pounds per square inch. It has been found that
when the necessary critical limits on water content in the
slurries is observed, these being different for the anode and
the cathode as noted, the deposition of the slurries is yreatly
facilitated, the leakage problems mentioned in the above-cited
Soltis patent are avoided, and very low internal impedances
and long shelf life can be attained without the application
of external compressive stresses.
Batteries comprising both positive and negative
slurry electrodes in accordance with the invention are
preferably made by a novel process involving the manufacture
of -three basic sub-assemblies. The first of these comprises
a sheet metal terminal to which is bonded a thin conductive
plastic current collector. To this laminate is bonded a
frame having a central opening exposin~ the conductive plastic
over a region defining an electrode site. A positive or
negative slurry electrode in accordance with the invention
is extruded into this opening to form a terminal electrode
asssmbly for the battery. The slurry deposit so made is
then covered with a separator.
A series of second sub-assemblies comprises an
intercell connector made from a thin sheet of conductive
plastic. This intercell connector is sealed over the central
opening in a ~rame such as that first mentioned, the borders
of which extend beyond the boundaries of the intercell
connector. Another deposit of slurry electrode of the first
kind is extruded into the opening in the frame over the
~08Z3~i
intercell connector. A separator is placed over this slurry deposi~. On
the opposite side of the assembly thus formed, a slurry deposit of a second
kind, opposite in polarity to the electrodes of the ~irst kin~, is made by
silk screening, extrusion or the like.
A third sub-assembly is made comprising an electrical terminal
made from a sheet of thin metal to which there is bonded a current collect~r
of conductive plastic such as that described above. On this laminate ~here
is extruded a slurry deposit of the second kind mentioned above.
Sub-assemblies of the second kind are stacked in series and on the
first sub-assembly described above, whereupon the third sub-assembly is
added to the stack. The composite assembly so formed is then sealed around
the edges to make a completed battery. By this process, thin, flat laminar
batteries can be made with considerably fewer steps than in production pro-
cesses practiced prior to the invention.
According to a broad aspect of the present invention, there is
provided in a method of making batteries with slurry electrodes, the steps
of sealing a conductive plastic intercell connector over a central opening
in a thermoplastic frame, extruding a first electrode slurry over the inter-
cell connector in the opening in the frame, covering the first slurry with
a sheet of separator material, and extruding a second electrode slurry in
registry with the first slurry over the opposite side of the intercell
connector from the first slurry.
The manner in which cells and batteries areconstructed in accordance ~ ;
with the invention, and considerations, governing the choice of materials
and proportions, will best be understood in the light of the following
.. : : .
detailed description, together with the accompanying drawings, of various
illustrative embodiments of the invention.
In the drawings,
Fig. 1 is a perspective view of a flat primary battery structure
according to the invention;
Fig. 2 is a sectional view of a battery structure according to the
invention taken through the plane 2-2 of Fig. l;
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.:
3Z30S
Fig. 3 is an exploded perspective representation of
the components of a battery structure according to the
invention, revealing the relative orientation of sheet-type
components thereof;
Fig. 4 is a chart comprising a family of curves
showing the shelf life characteris-tics of single primary cells
witn slurry cathodes of varying manganese dioxide to carbon
ratios;
Fig. 5 is a schematic block and flow diagram
illustrating components and processes schematically drawn to
show the manner in which thin, flat laminar batteries are
made in accordance with the invention;
Fig. 6, 7 and 8 are a series of schematic cross-
sectional elevational sketches, taken essentially along the
lines such as 6-6 in Fig. 5 but on an enlarged scale,
illustrating sequential steps in process of making a first
sub-assembly in accordance with the invention;
Fig. 9, 10, 11 and 12 are schematic cross-sectional
elevational sketches, again taken along lines such as 6-6
in Fig. 5 and illustrating steps in the process of making a
second series of sub-assemblies in accordance with the
invention;
Fig. 13 and 14 comprise schematic elevational
sketches, taken essentially along lines such as 13-13 in
Fig. 5, illustrating two stagas in the process of manufacturing
batteries in accordance with the invention; and
Fig. 15 is a schematic fragmentary cross-sectional
elevational sketch, on an enlarged scale, illustrating a
portion of a completed battery made in accordance with a
modification of the invention.
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~O~Z3~S
A multicell flat battery structure i9 presented
ge~erally at 10 in Fig. 1 as it would appear in an electro-
chemically active state following component build-up and
prior to final packaging. Features of the battery structure
apparent from th~s perspective view include an upwardly
- di~posed anode current collector assembly 12, the outwardly
facing surface 14 of which is fashioned of a metal to serve as
a t~rminal. Current collector assembly 12 is folded about
one side of battery structure 10 such that the terminal defining
portion 16 of surface 14, as revealed in Fig. 2 and in phantom
in Fig. 1, is located on the lower side of the battery. A
cathode electrode collector assembly 20 (shown in Figs. 2 and
3) is provided as the lowermosk component of the battery and
includes, in similar fashion as assembly 12, a metallic
outwardly facing surface portion 22 which also serves as a ;
terminal surface for the battery structure. With the geometry
shown, cathode and anode terminals may be provided in
convenient ad~acency on one side o the pile assembly. The
slightly depressed peripheral portion 24 of the assembly is
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occasioned from peripheral sealing procedures providing during - .
,. . .
assembly. This depression, as revealed in Fig. 2,
necessarily becomes more exaggerated in a sectional view
of the battery. Extending from the periphery of the battery
and ormed in the course of the sealing procedures, is an
outer border seal 26 formèd of a plurality of frame-type
sealing elements which extend inwardly from the border portion
shown to select laminar elements of the battery. This
lamination, as at 26, is relatively rigid, ~hereby contribut
ing to the structural integrity of the flat battery
configuration. y
~823~)5
Referring to Figs. 2 and 3, the geometry and
interrelationships o~ the discrete components forming battery
pile 10 are revealed in detail. As described above, the
exposed surfaces of the battery are present as an outer
laminate of current collector assemblies 12 and 20.
Prefabricated as discrete elements of the system, assemblies
12 and 20 are formed of a metallic sheet foil current
collector which, in turn, is laminated to an internally
disposed polymeric current collectorO In this regard,
assembly 12 is ~ormed having a metallic surface current
collector 14 serving as a terminal surface laminated with
a polymeric current collector 50 J while assembly 20 is
fonmed having a metallic current collector outer terminal
defining surface 22 laminated with polymeric current
collector 52. Each of the metal current collectors 1~ and
22 may be provided as an annealed tin coated steel sheet,
preferably about 2 mils in thickness; however, they also may
be ~ormed of aluminum or lead sheet material of similar
thickness for batteries intended for electronic photographic
use. Polymeric current collectors 50 and 52 ~ay comprise a
non-conductive matrix, for instance~ of a thermoplastic
material so thoroughly impregnated with conductive particles,
as of carbon, for example as to be effectively conductive.
For example, the polymeric layers of the battery may be made
from an electrically conductive carbon-impregnated vinyl film
sold under the trademark "Condulon" having a thickness on the
order of about 2 mils. for the instant application. As is
apparent, the assemblies are prelaminated together prior to
their assembly within the battery pile. Collector sheets
50 and 52 generally are impervious to electrolyte, are
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3~5
electrochemically inert and are characteri~ed in exhibiting
a low resistance to the flow of current from one face to the
opposite face thereof. Accordingly, discrete sheets of this
same material may be utilized for geometric cell definition
and additionally as intercell connectors within a series
build~up of cells forming a primary battery pile structure.
Considering the build-up of the pile structure, the
battery 10 is seen to be formed of four serially associated
cell units which are electrically associated but chemically
isolated by intercell connectors 54a-54c. I~he intercell
connectors preferably are formed as discrete rectangular
sheets of electrically conductive carbon-impregnated vinyl
film, as described earlier in connection with collector sheets
50 and 52, and, for the instant application having a thickness
on the order of about 2 mils. The peripheral integrity of the ~
entire pile structure is provided by a sequence of frame-shaped ; ~ -
border seals designated generally at 56a-56e. Being mutually
identically dimensioned, frames 56a-56e are formed having
inner borders which define rectangular inner openings which
mutually cooperate to form the peripheries of individual cell
cavities. Additionally J each of the frames is dimensioned
suc'n that it extends beyond the periphery of an associated
polymeric intercell connector 54a-5aA!c as well as the polymeric
surface portion 52 of assembly 20. As revealed in Fig. 3,
the frame 56e extends outwardly from three edges of the -
assembly 12. As noted from the drawings, the frames 56a-56e
are continuous and preferably are formed of a material heat
sealable both along their commonly juxtaposed surfaces in the
final pile structure as well as with polymeric collector
sheets 50, 52 and 54a-54c. Material for the frames should be
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Z305
electrolyte impervious, remaining inert to the chemical
activity of the battery structure. The frames 56a-56e may
be formed of polyvinyl chloride having a thickness, for the
present application, of about five mils. The thermal sealing
of the inner border surface areas to a corresponding polymeric
sheet, for instance, as at 52, may be carried out in impulse
fashion wherein the temperature of the sealed portion is
raised from room temperature to about 275F. and returned to
room temperature over an interval of about 15 seconds.
To form an initial one of the pile cell structures,
an initial collector assembly~ for instance~ cathode collector
assembly 20, may be preformed as a discrete assembly and a
frame member 56a may be bonded thereto as described above.
Over this subassembly is deposited, preferably by extrusion,
a positive aqueous slurry which is present as a particulate
dispersion of cathodic mix particles uniformly dispersed,
preferably in combination with a dispersing agent, with aqueous
electrolyte. In the preferred embodiment, the battery 10
incorporates a ~sclanche electrochemical system, accordingly,
thè cathodic material will be present as a particulate
dispersion of manganese dioxide and carbon dispersed within
an a~ueous ammonium chloride, zinc chloride and, additionally,
a small amount of mercuric chloride. The dispersant for the ;~
slurry is one selected to maintain a homogeneous character for
the dispersion therewithin and will exhibit a high tolerance
for salt as well as a stability from such effects as syneresis
or the like. A particularly desirable characteristic for the
dispersant is one which renders the slurry thixotropic, thereby
considerably facilitating extrusion type deposition procedures.
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~ ~ILQ15~X:30~i
Disper~ant~ whlch ma~ ~e ~ncorporated Ni~hin the
slnrries may be categorized as polymeric, synthetic resins
or natural gums, included in amounts, generall~ less than
one percent ~y weight of the electrolyte, selected to enhance
cohesiveness and extrudabilit~ without substantially degrad-
ing the electrical properties of the slurry. In effect, the
dispersion pro~ides for adequate in~erparticulate contact
to assure electrlcal conductivity while, at the same time,
providing a maximum exposure of particulate surface area to
ion conduction as derived fro~ the electrolyte component of `^~
the slurry. As examples of polymeric dispersing agents ef- ;
~ective for the development of the slurries of the invention,
mention may be made of meth~lcellulose ~sold under the trade-
mark "Methocel 4000" b~ Dow Chemical Co., Midland Mich.), `
poly-ethylene oxide ~sold under the trademark "Polyox" by
Union Carbide Corp., N.Y., N.Y.), hydroxyethyl cellulose
Csold under the trade~ark"Klucel" by Hercules Inc.,
Wilmington, Del.) heteropolysaccharide ~anionic) ~sold
under the trademark "Xanthan Gum" ~y~General Mills Corp.,
Minneapolis, Minn.), and poly-2-acrylamido-2-methylpropane
sulfonic acid. A natural gum dispersing agent which may
be utilized with the slurry system of the invention may be,
for example, guar gum derivative ~sold under the trademark
"Jaguar" by Stein, Hall ~ Co., N.Y., N.Y.~
The essential characteristic of cathode slurries
~n accordance with t~e invention is the inclusion of not
more than about 30 percent, nor less than abeut 23 percent,
of Nater, ~ased on the weight of slurry. Preferably, the
water content is from 26 to 28 percent by weight. Smaller
3Q amounts of water produce a mix that cannot be easily or uniformly
~ 12
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8Z3(~S
extruded, does not ~orm a cohesive layer in the battery,
and generally lead to low yields and poor shelf life and
perEormance. About 30 percent by weight of water is the
most that can be included before separation of the liquid
from the slurry is encountered, causing leakage and poor
seals which greatly reduce both yields and the shelf lives
of the survivors. The conditions in this regard are much
diferent from those encountered in flat Leclanche cells
des:igned for operation under pressure, as in the above cited
Soltis patent, in cylindrical Leclanche or alkaline cells,
which again are basically pressurized systems; in cells
designed for operation at very low temperatures; or in zinc
chloride cells.
In Batteries, Volume I, Manqanese Dioxide, edited
by Karl V. Kordesch and published by Marcel Dekker, Inc.,
New York~ New York in 1974, on page 155, various cathode mix
compositions for various current drain conditions in cylindrical
D cells are given. These range in water content from about
10 to about 16 percent, based on the weight of mix. Alkaline
cells are discussed in chapter 2 of the same book; since the
chemistry is quite different, notably in that alkaline cells
are anode dependent, whereas Leclanche cells are cathode
dependent; and in that Leclanche cells are acidic in pH,
whereas the alkaline cells have a very high pH; analogies
cannot readily be made. Very low temperature cells are
described, for example, in U. S. Patent ~o. 3,060,256, issued
on nctober 23, 1962 to J. W. Paulson for Low Temperature Dry
Cell. In this patent, the inclusion of lithium chloride in
the electrolyte, together with a moisture content as high as
36 percent by weight, are recommended. Such a formulation
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~Z305
could not be used for the purposes of this invention,
because of the separation and leakage problems described
above. Zinc chloride cells are described in the above cited
book, Batteries, on pages 213-215 and elsewhere, and a
par~icular example containing 25.6 percent of water in the
cathode mix i9 described in U. S. Patent No. 3,888,699~ ~
issued on June 10, 1975 to Lewis F. Urry for Primary Dry Cell. ~ ; :
These cells are not analogo~s to Leclanche cells, particularly
where water content is concerned, because the chemistry is
quite different. In particular, as set out on pages 214 and
215 of Batteries, supra, in the zinc chloride cell 9 moles
of water are consumed for each 8 moles of MnO2 reduced,
whereas there is no water loss in the overall reaction of
the Leclanche cell~ Moreover, the high impedance of zinc
chloride solutions would make their use utterly impractical
where very high current drains are needed.
The deposited positive aqueous slurries are
represented in the drawings at 58a-58d. Mote that the
slurry as at 58a is deposited over the surface of polymeric
collector 52 and corresponding cathodic slurries 58b-58d are
located for contact with an upwardly extending surface of an
appropriate intercell connector sheet 54a-54c. With this
arrangement~ the contacting polymeric surface serves as a
current collector for the associated positive electrode
structure.
It has been determined that for slurry cathode
electrode systems according to the invention, the ratio by
weight of manganese dioxide to carbon within the slurry may
be optimized. The curves of Fig. 5 provide an indication of
shelf life versus closed circuit voltage performance of
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cathode s-lurr~ unit cells ~ormed ~a~ing varying ratios of
manganese dioxide to car~on content. Each curve is labeled
wit~ that ratio wit~ which the unit cells deriving it were
fa~r~cated. For some structures, slgnlficantly improved
shelf life performance ma~ be achieved with ratios between
a~out 6:1 and 12:1. However, within this range, the most
preferred ratio for achieving improved shelf life for the
cells is 8:1.
Upon deposition, as by extrusion, of cathodic
slurry 58a, a selectively dimensioned sheet of batterr
~eparator material 60a is positioned thereover. This
material is selected as being wettable by the slurry de-
positions with which it is in contact as well as being
ionically permeable. Additionally, the material should
exhibit a texture or porosity, the interstitial openings
or channels of which are Oe adequatel~ fine geometry or
size to assure that no migration of the particulate matter
of the slurries from one electrode environment to another
may occur. Among the materials conventionally used as
separators, mention may be made of fibers and cellulosic
materials, woven or nonwoven ~ibrous material such as
polyester~ nylon, polypropylene, polyethylene or glass.
Specifically, a Kraft paper having a thickness o~ about
2.0 mils. has been found to be adequate for the purpose
of t~e instant application. However, the best material
for this purpose presently appears to be cellophane free
of humectants or plasticizers, as described in more detail
in United States Patent 4,119,770, by Edwin H. Land for
Electrical Cells and Batteries and assigned to the assignee ;
Oe this application.
15 -
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305
As shown in Figs. 2 and 3) separator 60a as well
as ~eparators 60b-60d are dimensioned as having the same
per~.pheral shape and size as polymeric collector 20 or
in~ercell connectors 54a-54c. In this regard, note that the
S separators are dimensioned such that their peripheries extend
over the inner rectangular openings defined by the inner
borders of frames 56a-56e.
The associated anode for the initial cell of the
pil~ structure illustrated is represented by a slurry deposited
over one surface of intercell connector 54a opposite and
generally coextensive with the deposition of cathodic slurry
58aO As in the case of the cathode slurxies, the anode slurry
as at 62a may be deposited utilizing positive displacement
techniques, doctoring, silk screening or the like, however,
considerable manufacturing advantage may be achieved inasmuch
as the slurry is of a consistency permitting its deposition '
by Qxtrusion.
Negative electrode slurries 62a-62d comprise a
particulate dispersion of metallic anode particles disposed
as in the case of the positive slurry, as a substantially
uni~orm dispersion within aqueous electrolyte. For a Leclanche
system, zinc particles are utilized as the active material
and are present in a concentration per unit area effective
to provide an electrically conductive dispersion thereof,
while the electrolyte is present in intimate surface contact
with the particles in a concentration rendering the slurry
ionically conductive. A zinc particle size of, for example,
about eight microns mean diameter may be utilized with the
slurry. The dispersing agent utilized for the slurry may be
selected to enhance deposition thereof. Those dispersing
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~Z30S
agents described above in connection with the formation of
the positive slurry electrode may be utilized for forming the
negative slurry electrode.
The essential characteristic extrudability and
coherance of anode slurries in accordance with the invention
are dependent on the amount of water included in the mix.
When the object is to form a smooth adherent layer on a
conductive plastic substrate by extrusion, silk screening or
the like, while achieving minimum impedance, conventional
techniques used in forming powdered zinc electrodes are not
satisfactory. It is highly undesirable for this purpose to
form the electrode with substantial proportions of a gelling
agent, as has been done in alkaline cells, for example,
because the impedance would be too high. Methods based on
placing the zinc powder in a pouch or envelope, as in the
above cited patent to Soltis, are inapplicable because
no mechanism i9 available in the laminar battery to hold the
powder in place during assemply. In slurries formed with
solutions of Leclanche electrolytes, zinc tends either to
ca~e up and form a crumbly mass that is not adherent to the
substrate, or to separate out of the li~uid. ~ small amount
of a wAter soluble polymeric suspending agent) such as
carboxymethyl cellulose, hydroxyethyl cellulose or the like,
is o~ material assistance in keeping the zinc powder in
suspension. On the other hand, the zinc and ammonium chloric~s
appear to act in opposition to the suspending agent in this
respect. It has been found that with an electrolyte solution `:
of typical low impedance concentrations of zinc chloride
and ammonium chloride, in which ammonium chloride predominates,
somewhat larger quantities of liquid, and consequently of
:
~17-
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~)8230S ~
watf~r, may be needed than in the cathode qlurries. In
particular, amounts o~ from 25 to 40 percent o water, and
preferably about 26 to 33 percent, of water, based on the
weight of ano~e slurry, produce mixes of good extrudability
and reasonable stability. All such slurries should be used
soon after they are prepared; standing overnight, for example,
will usually produce settling, caking or gassing.
The first cell build-up is completed with the
positioning in registry of intercell connector 54a over
negative slurry deposition 62a. Intercell connector 54a is
formed, as described above, incorporating a border sealing
frame 56b, the inner surface portion of which is thermally
bonded to the outwardly disposed surface of the intercell
connector sheet. Upon being so positioned to define the cell,
the outer peripheral border surface portions o E frame 56b
are thermally bonded with the corresponding outer surace
portion o rame 56a. In addition to serving as an intercell
connector, sheet 54a also serves as the current collector
for the negative electrode of the initial cell. Note that
within the initial cell, separator 60a extends not only
suficiently to separate the electrode slurries 58a and 62a
but also i9 configursd to provide electrical separation o~
current collector sheets 52 and 54a and to extend over the
thermal bonding surace between each frame member and its
associated current collector sheet. With this arrangement,
no inadvertent shorting 0fects or the like are likely to
arise. Eurther, such geometry assures that no migration
o the particulate dispersion o one electrode slurry into
the opposite electrode slurry occurs.
--18--
~OB~23~S
For production of a battery unit having a single
cell construction, cathode slurry material 58a is ~eposited
on current collector assembly 20 as described above.
Sep~rator shee,t 60~ then is positioned over the slurr~
following which anode slurry material is deposited upon the ,~
surface of pol~meric current'collector 50 of current collector
assembly 12. Border frames 56a and 56e then are heat sealed
together to complete the cell. This sealing may be carried
out by the above-noted impulse thermal bonding technique.
~o provide the multicellular pile structure, for
ins-cance, having four cells as illustrated in the drawings,
the pile build-up is carried out in a sequence next to be
described. In particular, the initial cell is fabricated as
abo~e by depositing cathode slurry 58a following which
separator 60a is positioned over in appropriate registry
with polymeric collector 52. Anode slurry material 62a then
is deposited upon one surface of intercell connector 54a and
the connector 54a as well as previously attached frame 56b
is joined with collector assembly 20 and thermally bonded
thereto at the adjoining surfaces of frames 56a and 56b.
Cathode slurry material as at 58b then is deposited on one
side o a next separator sheet 60b and the subassembly is
placed in appropriate registry upon the opposite side o
, polymeric intercell connector 54a. ~node slurry composition
then is deposited upon one side of another polymeric intercell
connector 54b. Intercell connector 54b, including previously
atk~ched rame 56c then is placed over the subassembly
inc:luding separator 60b following which frame 56c is thermally
bonded with frame 56b. This procedure essentially is
reiterated until the entire pile structure including anode
.
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108231J5
current collector assembly 12 is attached. Following desired
final thermal bonding of the entire stacked array of cells,
extended portion 16 of collector assembly 12 is covered with
an insulative tape 64 and wrapped around to the underside of
the battery to provide for juxtaposed terminal defining surfaces.
The battery assembly may then be mounted upon a supporting
card as at 66 having apertures 68 and 70 preformed therein to
provide access to the noted terminal defining surfaces.
The process of the invention just described will next
be more fully described with reference to Figs. 5 through 14.
Fig. 5 shows in a schematic fashion the several components of
the battery described above in their relation to a manufacturing
and assembly process in accordance with the invention illustrated
in block diagram form.
The process may be considered as divided into three
sub-processes, each of which results in the manufacture of a
subassembly, which subassemblies are then assembled to make the
completed battery. As indicated above, the first subassembly
comprises as starting material, the metal terminal 22 to which
is laminated the conductive plastic current collector sheet 52.
As illustrated in Figs. 5 and 6, the first terminal
assembly comprising the sheets 22 and 52 are bonded to a first
frame 56a of a series of the frames 56 de~cribed above in a
sealing statiorl indicated schematically at 100 in Fig. 5, so
that the conductive plastic sheet 52 is bonded to the whole
surface of the~frame 56a over the area indicated schematically
in Fig. 6.
A supply of the first electrode slurry, comprising
the material for making up the cathode slurries 58 in the
particular embodiment here described, is schematically indicated
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as disposed in a container 101 for distribution to various
ext--uders to be described, including in particular a ~irst
extruder 101. At the extruder station 101, the first cathode
slu.rry deposit 58a is deposited within the opening in the
frame 56a and over the surface of the conductive plastic
col:Lector sheet 52 as shown in Fig. 7. The extruder 101, and
other such devices to be described, may be any conventional
apparatus known in the art for this purpose. In a hand process,
the slurry could simply be deposited with a spatula using the
frame 56 as a màsk.
The subassembly illustrated in Fig. 7 produced at the
extruder 101 is next transfered to a station at which the first
of the separators 60, and particularly separator 60a is placed
ove:r the frame 56a and in contact with the slurry patch 58a as
shown in Fig. 8. I'he structure of Fig. 8 comprises the first
.
suhassembly discussed above.
The manufacture of a second series of subassemblies is . : ~:
carried out in process apparatus indicated generally at 103 in . :::
/ Fig. 5. At a first station 104 in the apparatus 103, one of
the intercell connectors 54 is sealed to one of the frames 56
`~ over a portion of the inner periphery of the frame 56 as shown
in Fig. 9. This process is carried out by the application of
heat and pressure in a conventional fashion either by any
conventional automatic processing apparatus or bv hand, with the
aid of a suitable manually operated heated press.
Comparing Figs. 5, 9 and 10, the framed intercell
con.nector 54 of Fig. 9 is transfered from the sealing apparatus
104 to an extruder 105 of any variety described above, in which
a slurry deposit from the first slurry electrode supply 101 is
deposited as indicated at 58 in Fig. 10. As suggested at 106 in
: .
305
Fig. 5, this asse~bly is then covered with one of the
separators 60 to produce the subassembly shown in Fig. 11.
The separator 60 will become wet by the slurry 58 when this
ope~ation is performed, assisting it in adhering to the
cathode slurry 58. If the separators 60 are made of a
conventional porous material, having their edges filled with
liquid impermeable, thermoplastic adhesive material, as
described, ~or example, in U.S. Patent No. 3,708,349, issued
on ~anuary 2, 1973 to William R. McCauley et al, for Method
of Constructing Multicell Batteries, the separator 60 may be
sealed under heat and pressure to the frames 56 at this stage.
This operation is actually not essential, however, because the
peripheral seal is entirely completed through the frames 5~. .
Referring now to Figs. S and 11, as the next stage
in the operation, the assembly from the covering stage 106 is
transmitted to an extruder 107 of the kind described above,
where a slurry anode deposit 62 shown in Fig. 12, is applied
from a supply of a second electrode slurry 108 indicated in :
Fig. 5. This operation completes the second subassembly, of
: 20 which three are required for a four cell battery.
It will be~apparent that because the apparatus 103 is
required to produce three subassemblies for each subassembly
produced from the cover stage 102, for high speed production as
many lines 103 would be de~irable as there were subassemblies
of the second kind to be made. In particular, for four cell
battery, three such lines 103 would be desirable. However, this
feature has not been illustrated as it would sufficiently be ?
apparent ~rom the description given and would undul~ complicate
the drawings.
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8230S
comparing Figs. 5, 8, 12 and 13 as the next step in
the process of assembly, one of the subassemblies of Fig. 12
fro~ the extruder 107 is stacked on top of the subassembly of
Fig. 8 from the cover operation }02 at a station indicated
schematically at 109 in Fig. 5. The result is as shown in
Fig. 13. This operation simply comprises placing frames 56a
and 56b in registry and bringing the components together.
This stacking operation is reiterated, as suggested
at 110, 111, and 112 in Fig. 5, until each of the three
subassemblies comprising the frames 56b, 56c, and 56d are in
place as illustrated in Fig. 14.
Manufacture of the third subassembly begins with the
second terminal assembly 12 described above. As illustrated in
Fig. 5, the plastic insulator sheet 64 may be heat sealed to
the conductive plastic sheet 50 as a preliminary ~tep, or it
may be added later as described above.
The second terminal assembly 12 is provided with a
sec~nd anode slurry patch 62d ~rom the supply of second
electrode slurry material 108 in an extruder 113 to produce a `
subassembly shown in Fig. 14 that is stacked with the other
components of the battery as suggested at 112 in Fig. 5 and
shown partly completed in Fig. 14. The assembled stack i5 then
passed to a final seal operation as indicated at 113 at which
the seals are aompleted around the entire periphery of the
~5 battery as described above.
As suggested at 114j the anode terminal may be folded -
over to bring the insulating sheet 64 into the position shown
in ~ig. 2, and the final packaging can be completed as
suggested at 115 in Fig. 5 and described in mor~ detail above.
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.. :.. , ., .... : . :
~L08;i~305
Fig. 15 shows a portion of a completed battery in accordance with
the modiEication of the invention particularly adapted for use with
separators ma~e of Cellophane, a highly impermeable she~t material made of
regenerated cellulose. The process of Figs. 5 through 14 may be employed
to produce this battery, the primary difference being in the relative sizes
of the separators and the intercell connectors.
In Fig. 15, parts are given reference characters corresponding to
parts with similar function in Fig. 2, with 100 added to the suffix. For
example, the frames are numbered 156a through 156d, rather than 56a through
56d. One exception to the numbering scheme just mentioned is that the outer
terminal steel 140 corresponds to the terminal 14 in Fig. 2.
One presently preferred material for the frames 156a through 156d
is *Versalon TPX 1140, a polyamide resin made by General Mills Corp. of
Minneapolis, Minn. These frames may be 18 mils thick in a particular embodi-
ment of the invention, designed to incorporate relatively thick cathode slurry
layers 158a through L58d.
The separators 160a through 160d in Fig. 15 are made smaller than
the intercell connectors 154a through 154c. When the separators 160 are
made of *Cellophane, this construction is preferred because the *Cellophane
becomes wet by the slurry and is not readily bonded to the other elements
in the battery. Thus, the intercell connectors 154 are carried out beyond
the separators so that they can participate in the seal formed between the
frames 156. In this manner, the integrity of the seal may be considerably
improved.
Various modiications may be made in the process in Fig. 5 without
departing from the scope of the invention. In particular, the first anode
slurry at 101 has been described as the cathode slurry because a Leclanche
system in the cathode slurry will generally be larger in size and weight
than the rather thin light anode slurry. Weights of slurry that have been
employed in practice are, for example, about 3.75 grams for the cathode and
1.3 grams for the anode.
* trade marks
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~IQ~Z30S
In other systems, such as alkaline systems which are anode dependent
rather than cathode dependent, the Eirst slurry might be the anocle rather than
the cathode. Another modification that might be made is to stack the sub-
assemblies from the extruder 107 before adding the subassembly from the cover-
ing up stage 102. Other alternatives of this kind will be apparent to the
artisan and need not be described in detail.
Specific anode and cathode slurry compositions for use in practic-
ing the invention are more ~ully described in the above cited U.S. Patent
No. 4,119,770 and in U.S. Patent No. 4,105,815 ~Buckler).
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Z3(~5
(rola~oid Caae ~lo.~--5G3~ Briefly, suitable compo~itions are
given in the following examples, in percent by weight based -
on the total weight of composition.
EXAMPLE I
Weiaht ~t. %
Methocel 4000 2 gm. 0.33
ammonium chloride 68 gm. 11.24
zinc chloride30.9 gm. 5.11
mercuric chloride5.9 gm. 0.98
powdered zinc300 gm. 49.60
water 198 ml. 32.74
100 . O
In the above ~ormulation, Methocel 4000 is
carboxymethyl cellulose, as sold by Dow Chemical Co. of
Midland, Michigan.
EXAMPLE II
Weight Wt.~
ammonium chloride ~33 gm. 8.66
zinc chloride 15 gm. 3.94
mercuric chloride3 gm. 0.79
poly-2-acrylamido-2-
meth~lpropane sulfonic acid 6 gm. 1.58
carbon black 25 gm. 6.56
manganese dioxide 200 gm. 52.49
water 99 ml. 25.98
100. 0
EX~MPLE III
Zn 60.00
H2O 25.98
Carboxymethyl cellulose0.26
HgC12 0.78
NH4C1 8.92
ZnC12 4.06
100. 0
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~08230S
EXAMPLE IV
Zn 50.03
H2O 31.70
NH4C1 10.49
HgC12 0.68
Jaguar gum 2.10
2 5.00
100 ~ O
E%AMPLE V .
lQ Zn 76.4
H2O 15.0
NH4C1 5.0
~gC12 1. 0
ZnC12 2.3
Carboxymethyl cellulose O.3
100 . O
EXAMPLE VI
zn 54.40 ~ .
H20 30.31
ZnC12 4.36
NH4C1 9.36
HgC12 0.71
: hydroxyethyl cellulose 0.87
~ ' .
EXAMPLE VII
Zn 47.1
H20 37.2
: ZnC12 3.4
NH4C1 10.7
HgC12 0.6
hydroxyethyl cellulose 1. 0
00. 0
:
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.
~)8Z30S
E~MPLE VI I I
NH4C1 8 . 78
C12 3. 99
HgCl 2 0 . 8 0
Poly-sulfonic acid1.60
Carbon 6.65
H2O 25.00
Mn2 s3 19
EXAMPLE IX
Carboxymethyl cellulose 0.3
Zinc 60.0
Water 26. 0
HgCl2 0.8
NH4Cl 8.9
ZnCl2 .
1 0 0 . 0 :
~' ', .
EXAMPLE X
% ~:
MnO2 51.81 . :~
Carbon black 6. 48
ZnC12 4 - 35 !'
NH4Cl 9.56 . :
H20 27.80
100.0
While the invention has been described with reference
to the specific details of various illustrative embodiments,
many changes and variations will occur to those skilled in the
art upon reading this description. Such can obviousl~ be :
made without departing from the scope of the invention.
Having thus defined the invention, what is claimed is: :
~ '.
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