CA1047103A - Conductive coated vented cathode collector for thin flat cells - Google Patents

Abstract

CONDUCTIVE COATED VENTED CATHODE
COLLECTOR FOR THIN FLAT CELLS

ABSTRACT OF THE DISCLOSURE

A thin flat cell employing a metal anode (zinc), a cathode (manganese dioxide), an electrolyte (ammonium chloride) and a perforated cathode collector (steel); said cathode collector being coated with a continuous layer of a gas-permeable, electrolyte-impermeable polymeric material which allows the venting of undesirable gases formed within the cell while preventing any electrolyte loss from said cell.

S P E C I F I C A T I O N

1.

Description

~ ~7 ~ o 3 Field of the In~ention This invention relates to an improved construction for thin fla~ cells or batteries and particularly to thin flat cells or batteries employ-ing a vented cathode collector.

Descri tion of the Prior Art P

- The continuing development of portable electrically powered devices of compact design such 8 tape recorders and playback machlnes, radio trans-mit~ers and receivers, sha~ers, watches, and motion picture or 8 till cameras creates a conti~uing demand for the development of reliable, compact batteries for their operation. The power needs of such devices are varied. Thus, a watch requires a battery which will perform uniformly for at least a year at low drain; recorders and radios require batteries which will operate intermittently for perhaps a half hour ; ~o several hours a~ substan~ially higher drains followed by longer periods of non use. A motion picture camera in which a battery may operate expo~ure control means as well as drive a motor ~ually requires the bat~ery to operate in a repet~tive serie~ of relatively ~hort periods of ~ime in a gi~en day, but m~y not be used for weeks ~ 73L~)3 9383-2 or months. A still camera in which a battery may be used to fire a fla~h bulb and in ~ome ca~es to control exposure means and advance the film after each exposure requires the battery to deliver a serie~ of pulses of rather high current, frequently in rapid ~ucces~ion.
While the battery indu~try has been quite succes.sful in providing bat~eries to sa~isfy these diverse demands, the vast ma~ority of the batteries produced for and used in devices of the type discussed are cylindrical. Theymay range in height from the amiliar "button" cell~ to as much as one-half inch to one inch or even more and in diameter from roughly about one-half ~nch to one inch or more. Although they are excellent sources of elec~rici~y, their shape has limited to 80me extent the size and shape of the devices for which they are intended. As design concep~ change there 16 increasing emphasis placed on thin, flat ~hapes.
Devices of thin, flat shape cannot be made ~o accommodate the familiar cylindrical batt~ry without devo~ing ~ore ~pace to th~ battery than ~s de~ired. APcordingly, there iB an increasing demand for thin, flat batteries.
The problem aæsociated with maintsining good electrieal contact between cell el~ments i~ psrticular~y notable i~ thin fla~ cell con~truc~ions where external $upport8 are generally i~practical since ~uch ~mbers ~y be ~ny ~im~ ~he thickneas of the cell lt~elf. In addi~ion~ since 8uch flat cell~ po~6eæ~ ~ large ~m6upported ~ ~047103 9383-2 surface, the usual ~eans employed for maintaining cell integrity along the periphery of the cell may not be ~ufficient to main~ain good electricsl cont~ct between cell elemen~s at the center of the flat cell bec~use of the fornation of gases wi~hin the oell which ha8 a tendency to 6eparate the cell components thereby increasing the re~i~tance of the cell to ~ degree that the cell could become inoperative for itS lntended u~e.
: It has previou~ly been suggested in ~he prior flat cell art that adhesive~ be used in assembling specific cell componenta, for example, between cathode and cathode collector, between collector and the outer envelope, and between cel~s in a stack. These bonding techniques are se~ orth in d¢tail in U. S. Patent Nos. 2,870,235 to Soltis, 3,379,574 to Grulke et al, 2,762,858 to Wood, 1, 3,223,555 to Solo~on et al, 2,658,098 to Coleman et al and 2,487,985 to Ruben. The adhesives described in these patents have been suitable for use only ~n a limited por-tion of the cell and could not be used to maintain the entire cell structure a~ an integral unit. For example, : none o the adhe~ive~ previously ~uggested has been entirely ~ui~able or u~e in providing permanen~ adhesion to the eorroding face of the cell anode. In thi~ connection, it i8 well known that during discharge of the cell, the anode metal i~ con~u~ed, ~nd if consumed in a non-uniorm ~anner, phy~ical void~ could occur on and in the anode ~urface.
Proper we~ting of the ~node ~urf~ce by the adhel~ive ~ust be 4.

1~471~3 9383-2 maint~ined for the adhesive eo be efective.
U. S. Patent 3,563,805 to Deierhoi, Jr.
disclo~e~ a flst cell ha~ng an anode" a cathode, a separator, an immobilized adhesive electroly~e and a cathode collector, all of which sre appropriately arranged and adhesively secured together by a conven-tional ~ealing mesnR which effecti~el~y ~aint~ins a relatlvely l~w electrical resistance contact between all the individual cell component~.
In U. S. P~tent 3,617,387 to Grulke et al, a flat cell i~ disclosed which haB all its comporlents completely internally bonded ~ogether ~ith a polymeric adhesive, said sdhesive maintaining physlcal and electrical contact between the c~mponents.
Another approach to produce a flat multicell bsttery i~ disclosed in U. S. P~tent Nos. 3,770,504 to Bergum et al and 3,/70,505 to ~ergum, wherein the con-fronting faces of each ad3acent pair of conductive layers forming the battery are adhered and electrically bonded 20 one to the other. In addition, ad~acen~ cells of the battery are electrically connected one to the other by means o~ an electrolyt~ impenviou~ intercell connector layer which extends beyond the electrode~ of the sells so that the peripheral faces of the intercell connector layer~ clm be auitably sealed to provide a liguid im-perviou~ seal around each cell.
Although all of the above approaches ~ork to 5.

:1047~(~3 ~ome degree in producing a flat cell, a buildup of undesirable gas pressure generally occurs within a cell during shelf storsge or during discharging which could be ~ufficient to separate two or more of the cell's components thereby greatly increasing the internal resistance of the cell to a point where the cell becomes ineffective for its intended use.
U. S. Patent No. 3,901,732 issued to T. Kalnoki-Kis and T. A. Reilly discloses another approach to producing a thin, flat cell or battery wherein the anode of the cell i~ perforated for the purpose of venting undesirable gases formed ~uring storage and discharge of the cell or battery. This patent application al~o discloses an e~bodiment wherein the anode and the cathode collector are both perforated for venting undesirable gases found within the cell or battery.
It is an ob~ect of the pre~ent invention to provide a thin, flat cell or battery having novel means for venting undesirable gas formed within the cell 80 as to eff~ctively minimize any gas pres~ure buildup within the cell.
Another obJect of the present invention is to provide a thin, flat cell or battery having a perforated cathode collector which i8 coated on at lea~t one side ~ith a continuous layer of a gas-permeable, elec~rolyte-.
impermeable conducting adhesive or paint.

47~3 Another object of the present invention is to provide a thin, flat cell or ba~tery having good ionic and/or electronic conductivity at the interfaces of each of the cell's components throu~hout ~torage and discharge of the cell.

SummarY of the Invention The inventlon relates to a thin, flat cell having a me~al Enode; a cathode of depolarizer mix;
an electrolyte permeable ~eparator between said anode and sa~d cathode; an electroly~e in contact with said anode and said cathode; a~d a cathode collector; said cathode coll~ctor having a plurality of openings for venting undesirable gases formed in the cell and said cathode collec~or having on at least one of its surfaces a substantially continuous layer of a gas-permeable, electrolyte-impermeable conduct~ve paint;
and wherein said cathode, ~aid separator, and said electrolyte are bou~ded by a peripheral frame of electrolyte impervious sealing material, ~aid frame being bonded to at least a portion of the inner marginal faces of ~he anode and ~he coated cathode collec~or which ex~end~ beyond the area defined by said cathode, ~aid separator and said electrolyte.
The in~ent~on also relate~ ~o a t~in9 1a~

cell having a metal ~node; a eathode of depolarizer mix; ~n electrolyte permeable ~eparator between sald 7.

93~3_~;
~047~L~3 anode and said cathode; an electrolyte in contact with said anode and said cathode; and a cat~ode collector; said ca~hode collector having a plurality of openings for venting undesirable gases in the cell and said ca~hode collector having on at leas~ one of its surfaces a substantially continuous layer of a gas-permeable, electrolyte-impenmeable conductive paint; and wherein all of said components of said cell are ~ubstantially adhesively secured together so as to ma~ntain a relatively low electrical resist-ance contact between said individ~al cell components.
As used herein, a substantially continuous layer shal~ mean at least a layer that effectively cover~ the openings on the ~urface of the cathode collector, and when the material of the cathode col-lector is such that ~t would be subject to exces~ive corro~ion in a cell environment, then at least the ~urface of the cathode collec~or ~ub~ect to such cor-rosion will be substantially covered with the layer.
Preferably, the paint for the cell's cathode collector ha~ to be a gas-permeable, electrolyte-impenmeable cond~ctive paint~ as for exRmple, disclosed in U.S. Patents 2,759,038, 2,745,774, 2,834,826, 3~072~558~ 3a353~999~ 39343~995~ 3~510~448~ 3,563~851, 3,547,771 and 3,575,905. An additional paint or ~dhesi~e for use in this invention could compriæe a solution of a copolymer of v~nyl chloride and v:Lnyl ~cetate i~ an orga~ic solven~ containing a ~uitable ntabilizer for high temperature conditions ~nd a ~47~3 9383-2 plasticizer for fLexibility.
In one e~bodiment of thi~ invention, the cell's separ~tor, electroly~e and ca~hode of lepol~rizer mix are bou~ded at one end by a metal lmode and at the other end by a metallic cathode collector, said ~ode and cathode collector extending beyond the area def~ned by the cathode, separator and electrolyte thereby forming a perip~.eral reces~ between the marginal inner faces of said anode and said cathode collector into which a frame of electrolyte impervlous ~ealing material is deposited.
In thi~ type cell construction, any gases formecl during storage or durlng discharge of the cell will have a ten-dency to sep~rnte the components of the cell; ile., the cathode col~ector fr~m the cathode, or the separator fr~m the ano~e, which will have the effect of increa~ing the internal resist~nce of the cell to a degree that the cell may become inoperat~ve for its intended use. According to th~ 6 invention, a plurality of openings are placed in the cathode collector forventing any undesir~ble gases formed within the cell. In addition to perforatlng the cathode collector, a gas-penmeable, electrolyte-lmpermeable conductive coating i~ deposited on at lea~t one side of the cathode collector, pre~erably the ~ide cvntac~ing the cathode component of the cell~ ~o as to prevent the los~
o any electrolyte through the open~ngs in the cathode collector while allGwing for the e~cape of undesirable &~e~. By having the combination of ~ perfora~ed oathode collector-~nd 8 layer of ~ ga~-perme~ble, elecl~rolyte-imper~eable conduc~ive coating on ~aid cathode collector~

3 g38~2 the bonding 6trength provided by the peripheral frame of electrolyte imperviouc sealing material will be suffi-cient to main~ain the physical and electrlcal contact between ad~acent oell components during cell storage and discharge since any gases formed within the cell will be able to escape through the openings in the cathode eollector. Thu~ according to this invention, all compo-nents of the cell are secured in intimate contact, and no external pressure-exerting means need be employed. The fra~e of sealing ~aterial zurrounding the cathode, separator ant electrolyte, aids to rigidify the cell and in maintaining low electrical resistance contacts between the cell components in cooperation with the metal anode and the cathode collector to which the frame of sealing material i~ marginally ~ealed.
The size of the opening in the cathode collector can vary between about 10 microns in diameter and about 250 microns in diameter, preferably between about 75 microns in diameter and about 175 micron~ in diameter.
Openings larger than 250 microns in diameter will be un-~uitable because of the tendency of the gas-permeable, electrolyte-impermeable conductive adhesive to shrink and crack on drying~ thereby providing openings through which the electrolyte can escape. Openings smaller than 10 microns in diameter will be unsuitable bec~use ~he par~
ticles of the conductive material may be ~uffioiently large encugh to plug or ~ubstantially plug the openings thereby preventing ~he effective venting of the Igases 10. ~ , ~ 3 9383-2 fonmed within the cell. In addition, it would be diffi-: cult using conventional perforating means to form open-ings ~maller than about 10 microns.
The opening instedd of being circular c~n be square, rectangular or any ~hape RS long a~ the ~ize of the opening i8 between about 78 square microns and about 65,000 sq~are microns (~ 0.0006 cm2), preferably between about 4200 square microns ~0.00004 cm2) and about 25,000 square microns (~ 0.00025 cm2). In some instances, it may be feasible ~nd advantageous to impart slit~ in the cathode collector with any ~harp instrument, such slits being at lea~t about 0.0025 centimeter9 prefer~bly ~bout 0.0075 cent~eter,in width and up to about 1.0 centimet~r in length.
The number of openings in the cathode collector can vary depending on fiuch feature~ as the cell sy~tem and the poro~ity of the cathode mix. However, a minimum of at least one opening every three square centimeters of the cathode collector i~ nece~sary if ~he gases formed within the cell ~re to escape without di~rupting the contact between the cell component6. The maximNm number of opening~ in the cathode collector w~uld be limited to the number ~hereby the cathode collector would effectively lo~e it~ conductive characteristics and/or integrity and strength required ~o ~a~ntain ~he eell a~ a ~tnlctural pvwer unit. Preferably, the openings should be uniformly di~posed tbroughcut ~he cathode colleetor and~ ~here not ~ 0~7103 9383-2 ~niformly dispo~ed, the openings ~hould be dispo~ed at or near the center of the cathode collec~or where mechanical ~upport is ~t a minimum.
It iB apparent that if a rather dense, low poroGity c~thode mix ls u~ed in the cell~ then the number of openings in the cathode collector would have to be rather large to in~ure that any gas reaching ~he interface of the cathode mix and coated cathode collector wil:L
have an opening di~posed in the cathode collector through which it can escape. On the other hand, when a rather porous cathode mix iB employed, then the number of openings required would not be great since ~ny gas reaching the inter~ace o~the c~thode m$x and the coated cathode collector could easily c~rculate to an opening and e~cape therefrom.
When employing a rather dense cathode mix, the mix may be scored, perforated or suitably divided 80 as to provide adequate gas channels or passages within the mix leading to the interface of the cathode mix and the coated cathode collector.
Another ~mbodiment of this i~ven~ion would be ~l~ilar to the above-described cell conBtruction except that ~he anode ~nd cathode collector ~ould not extend beyont, but would be coextensive with, the area defined by the ~epsxator, electrolyte and cathode ~ix. In addition, all the cell components woNld be adhe~lvely ~ecured together a~ d~sclosed, for example, in 12.

~ 047~(~3 9383-2 U. S. Patent6 3,563,805 and 3,617,387. l~he additional requirement tha~ the adhesive means eDsployed to secure the cell components together be ga~-permeable i6 nece~sary 80 a8 ~0 ~llow any ga6 formed within t:he cell to cir-culate to the openings in the cathode collector. In this e~bodiment, all of the component~ of the cell are substantially adhesively ~ecured in intimate contact so that no external pres~ure-exerting means is necesssry.
Another embodiment of this invention would be a multicell battery comprising an outer negative (anode) electrode; an outer positive ~cathode) electrode; at least one duplex electrode between the outer positive electrode and the outer negative electrode; a ~eparator and an electrolyte between each positive and negative electrode in the battery; and a cathode collector having a plurality of openings for venting unde~irable gases formed within the battery a~d having on at least one of its surfaces a ~ubstantially continuous layer of a gas-permeable, electrolyte-impermeable conductive paint;
~aid duplex electrode compri~ing a po~itive electrode bo~ded to a porou~ negative electrode vi~ an electronically conductlve layer of a gas-permeable, electrolyte-imper~eable adhe~ive; and all o$ said components of ~aid battery ~ecured together 80 as to maintain a relatively l~w electrical regi~ance contact between ~aid individual cell components.
The posi~ive electrode, electrolyte ~mcl separator o each cell could be bounded by a peripher~l fr~me of electrolyte-impervious ~e~ling material ~hich cou}d 8180 be marginally bonded to each negat.Lve electrode and the ad~acent conductive layer of the dulpl~x electrode or the cathode colleetor defining each ~uch cell. Or, if desired, all of the components of the battery could be substantially adheslvely secured ~cogether as di~closed in U. S. Patent Nos. 3,563,805 and 3,617,387. If the latter construction i8 employed, then all the adhe~ive layers would have to be gas~permeable so as to permit any gases formed within the cell to circulate to the c~thode collector whe're they could be vented.
There are m~ny conductive ~dhe~ive3 or pa~nts which have been used, or are ~uieable for u~e, in the battery industry for bonding cell component~ together or for providing ~ cell component with a conductive l~yer. Examples of conductive adhesives or paints suitable for use ln this invention are set forth in U. S.
P~tent ~09. 2,759"038, 2,7h5,7749 2,834,826, 3,072,558, 3~353~999) 3,343,995~ 3,510,448, 3,575,905, 3~563,851 and 3,547,771.

1~ .

. ~471(~3 Plasticizers, including those materials which function as both a plasticizer and as a stabilizer, should be added in a minor amount to a c:onductive adhesive or paint to obtain specific chemical and mechanical properties desirable for a p~rticular application. For example, stabilizers are generally added to maintain chemical stability at high temperatures and in oxidizing environments. Plasticizers are generally added to impart viscoelastic properties to the formed film. In many cases, a single material will function both as a stabilizer and as a plasticizer when added to the copolymer of this adhesive or paint.
To render the a & esive or paint conductive, some electrically conductive particulate material, such as acetylene black, graphite or mixtures thereof, should be added. Preferably, a mixture having a ratio of 1 part by weight acetylene black to 3 parts by weight graphite would be suitable for most applications.
For use on the cathode collector in accordance with this invention, the adheslve or paint would contain the conductive material.
Brief Description of ~he Drawings Fig. 1 is an isometric view of a cell made in accordance to this invention.
Fig. 2 illustrates a par~ial cross-section of a cell wherein the components of the cell are shown greatly ~agn~fied for purposes o~ illustration.

938~2 ~047~0~
Fig. 3 ~llustrates a partial cross-section of a battery wherein the componen~s of the cell are shown greatly magnified.
Fig. 4 is ~ cross-section of ~nother embodiment of a cell wherein the components of the cell are shown greatly magnified.
Referring in more detail to the drawings, there is shown in Figures 1 and 2 a ~hin, flat cell 1 having an anode 3, electrolyte impregnated separator 5, cathode 7, cvnductive layer 9 and vented cathode collector 11.
Electrolyte impregnated separator 5 and cathode 7 are contained within and bound by anode 3 and cathode collector l~forming ~ peripheral recess 13 which is filled with a frame of sealing material 15 which m~rginally bounds cathode 7 and i~ secured to the inner marginal face 1/ of anode 3 and the inner marginal face 19 of cathode collector 11 via the c~nductive layer 9. The adhesive used to form the frame mNst not react with the cell components or reaction products, should be electrolyte-proof and impermeable to water and vapor transfer, antshould retain these properties and ~ts adhesivity over the r~nge of cell tem~erature operations. Su;table adhesives which can be used as ~he sealing material include the conventional vinyl adhesives or hot melt adhesives of vinyl-wax mixtures.
Cathode collector 11 i8 ~hown as having openings 21 for venting any unde~irable ga~es for~ed 16 .

~4~7~Q3 g383-2 within ~he cell during storage or discharge. The com-position o~ conductive layer 9 is as described above and i~ ch~racterized a8 being ga~-permeable and elecerolyte-impermeable. Thu~ sny gase~ formed at the vicinity of the anode can travel through the catholde 7, conductive layer 9 and out through opening 21 in cathode collector 11.
If desired, although not shown, a conductive tab, s,ecured to anode 3 or an exten~ion of anode 3, may be used as the anode termin~l for specific applications ~uch as when a non-conductive coating i~ applied to the outer ~urface of the snode.
To provide a battery of cells, it is necessary merely to piace the anode of one cell in intimate elec-tronic contact with the cathode collector of ano~her thus effecting a series connection.
Generally, the surf~ce contact pressure between the anode and the cathode collector of two ad~acent superimposed cells required to provide good electronic contact therebetween will be insufficient to block venting from the cathode collector. However, if desired, additional hor~zontal venting passages may be disposed between said component~ of the sd3acent cell~O
An alternate construction for a serie~ ~ack battery iB one having a "duplex" electrode in which one ~ur~ace of a ~etal anode i8 provided wlth ~n ~lectroni-cally conduc~ive co~ting ~ccording to this invention and ~ ~hown ln Figure 3.

17.

~ g3~3-2 ~7103 As seen in Figure 3, two cells are arranged one above the other and adhesively secured together.
The upper cell 30 comprises an anode 34, impregnated separator 36 and cathode 38. A conductive layer 40 9 as described above for layer 9, is disposed between, and bonded to, anode 42 and cathode 38. The lower cell 32 comprises a porous anode 42, such as powdered zinc, impregnated separator 44 and cathode 46. Disposed between cathode 46 and cathode collector 50 is conductive layer 48 which is identical to the conductive layer 9 of Figure 2. The perlpheral recesses 54 and 54' are filled with a sealing material 56 and 56', respectively, as described in conjunction with Figure 2. Cathode collector 50 is shown as having openings 52 for venting gases formed within the cell during storage and discharge.
A requirement for this type battery construction is that conductive layers 40 and 48 be gas-permeable so as to permit the gases within the cell to circulate to the opening~ 52 in the cathode collector 50.
Figure 4 shows another embodiment o~ a cell of this invention where~n all of the cell c~mponents are substantially adhesively secured together as disclosed, for example, in U. S. Patent Nos. 3,563,805 and 3,617,387.
Specifically, cell 41 comprises an anode 43, a first layer 45 of immobilized electrolyte, a separator 47, a second layer 49 of immobilized electrolyte, catho~e 51, a conductive layer 53 and cathode collector 55 having 18.

~~47~03 openings 57. The layer~ 45 and 49 of immobilized electrolyte provide the electrolyte which is in ionic or elec~rolytic contact with the anode and cathode of the cell. The electrolyte in this em~odiment can be a viscou~, tacky or "~ticky'l mass which can be held within the bounds of the cell by having a suitable electrolyte-impermeable coating placed around the side~ of the cell.
This mass, in addit~on to providing the electroly~e of the cell, will s2rve to hold the cell components together.
The preferred embodiment of this invention would employ the LeClanche electrochemical system com-prising mangane~e dioxide positive active material, zinc negative acYlve material, preferably sheet zinc, and ~n'electrolyte comprising ammonium chloride and/or zinc chloride. The cathode collector could be any conducting m~terial such as s~eel, copper, æinc, nickel and nickel alloys, Grafoil* and the like, preferably steel because of it~ relatively low C08t and good physical properties, such as strength. The perfor~ted cathode collectors of this invention, i.e., cathode collectors having a plurality of opening~, could be porou~ conduc~ive sub-str~tes h~ving pores within the range o ehe openlngs specified above. Examples of such materials are c~m-pre~sed ~etal w0018, sintered metal~ and ~he likle.

*Gr~foil 1~ a trademark for flexible graphite material of exp~nded graphite pa-ticles campres~ed togetherO
Gr~foll i~ manufactured by Union Csrbide Corporation, New Ynrk~ ~ew York and i~ the sub3ect ~at~er of U. S.
P~tent No. 3~4Q4D061.

19.

. ~ 4 ~ ~ o 3 9383_2 Although the preferred electrochemical system is LeClanche, there are a wide variety of electrochemical systems that can be used in this invent:ion. Among the positive electrode materials that are ~uitable for use in this invention are such materials a~3 manganese dioxide, lead dioxide, nickel oxyhydroxideg mercuric oxide~ silver oxide, inorganic ~etal halldes such as silver chloride and lead chloride, and organic materials which are capable of being reduced such as dinitroblenzene and azodicarbonAmide compounds. Among the negative electrode materials ~hat ~re suitable for use in this invention are zinc, zinc-clad steel, aluminum, lead, cadmium and'iron. Suitable electrolytes are ammonium chloride and/or zinc chloride, various alkaline electro-lytes ~uch as the hydroxides of potassium, sodium and/or lithium, acidic electrolytes ~uch ~s aulfuric or pho~phoric acid, and non-aqueous electrolytes, said electroly~es being chosen to be compatible w;th the negative and positive electrodes. The electrolytes may be either ~elled or liquid depending on the particu-lar cell con~truc~ion and the electrochemical system used. The sep~rator ~ay be ~ade from a wide varle~y of m~terials including the fibrous ~nd cellulosic m~terials which are conventional in battery construction a!; well as from wo~en or non-woven fibrous materi~l~ such as polye~ter, nylon, polyethylene and gla~, Preferred electrochemical systems for use in 20.

. 93~3-2 ~L~)4~(J 3 this invention are those in which the positive electrode comprises manganese dioxide, the negative electrode comprises metals such as zinc, zinc-clad steel or aluminum, and the electrolyte substantia:Lly comprises an acidic solution of inorganic salts. L~nother preferred electrochemical sys~em is the alkaline manganese system in which the positive electrode comprises manganese dioxide, the negative electrode comprises zinc, and the electrolyte substantially comprises a solution of potassium hydroxide. Other aqueous electrolyte systems suitable for use with this invention are nickel-zinc, silver-zinc, mercury-zinc, mercury-cadmium and nickel-cadmium EX~MPLE
Thin flat LeClancé cells, as shown in Figure 2, were prepared using a positive electrode mix of manganese dioxide, graphite and acetylene black, a negative zinc sheet electrode, and an electrolyte of ammonium chloride and zinc chloride. A cellulosic separator was disposed between the zinc anode and cathode mix of each cell as shown in Figure 2 and was saturated with the electrolyte of each cell. A vinyl gas-penmeable, electrolyte impermeable conductive paint, comprising a solution of a copolymer of vinyi chloride and vinyl acetate in an organic solvent containing a piasticizer, an epoxy resin stabilizer and a conductive particulate material of acetylene black and graphite, was applied ~o one surface of a steel cathode collec~or plate having openings disposed therein. After ~he paint dried, the coated cathode collector was assembled wi~h the other cell components, in a manner as shown in Figure 2, 21.

~ 71(~
and then a hot melt adhesive, obtained commercially as Swift Z-863 from the Swift Compa~y, was dep~sited in th~
peripheral recess formed between the extending anode and cathode plates to produce a thin rectangular flat cell.
~.ach cell measured 1.75 inches wide and 2.75 inches long with thc a~tiv~ ca~hode mix component o~ each cell measuring 1.48 inches by 2.25 inches.
Each cell was then tested by being success~vely discharged across a 0.312 ohm load for 0.1 second, a 0.832 ohm load for 1.5 seconds and then across a 6.250 ohm load for i.o second. This cycle of discharge was repeat~d after a three-second rest period until the closed circuit voltage of the cell decreased to 1.08 volts, The data obtained from the cells are shown in Tabl~ 2.

Open Circuit Voltage No. of Cycles Conditcon (avera~e3 No. of Cells~ (avera~e) 25C. . 1.65 volt~ 100 35 (fresh) : 120F. 1.6 volt~ 3 26 (2 weeks) 140F. 1.6 volts 5 16 (8 hours) 32F. 1.65 volts 3 5 (24 hour~) *The a~erage ~pedance of the cell~ w~s found to be ~tw~en 2 ~nd 2.5 o~m~ at l-kHz.
' 22.

~47~at3 It is thus shown by the above examples that using the teachings of this invention, flat cells can be constructed which can function under various tempera-ture conditions to deliver a series of pulses of rather high current in rapid succession.
It is to be understood that other modifications and changes to the preferred embodiments of the invention herein shown and described can also be made without departing from the spirit and scope of the invention.

Claims (5)

WHAT IS CLAIMED IS:

1. A thin, flat cell having a sheet metal anode; a cathode of depolarizer mix; a separator between said anode and said cathode; an electrolyte in contact with said anode and said cathode; and a cathode collector; said cathode collector having a plurality of openings for venting undesirable gases formed within the cell and having on at least one of its surfaces a substantially continuous layer of a gas-permeable, electrolyte-impermeable conductive paint; and wherein all of said components of said cell are substantially secured together so as to maintain a relatively low electrical resistance contact between said individual cell components.

2. The claim of claim 1 wherein the openings in said cathode collector are sized between about 78 square microns and about 65,000 square microns.

3. The cell of claim 2 wherein the openings are sized between about 4200 square microns and about 25,000 square microns.

4. The cell of claim 1 wherein said anode is zinc, said cathode comprises manganese dioxide, and said electrolyte comprises ammonium chloride.

5. The cell of claim 1 wherein said anode is 24.

zinc, said cathode comprises manganese dioxide, and said electrolyte comprises zinc chloride.

25.