CA1263697A - Alkaline cell container having interior conductive coating - Google Patents

Abstract

ALKALINE CELL CONTAINER HAVING INTERIOR CONDUCTIVE COATING

ABSTRACT OF THE INVENTION
A coating for the interior of alkaline cells is provided, so that a coated cell container or can may have a cell depolarizer inserted into the can without scraping the coating off the interior surface in any substantial amounts. The coating includes carbon particles (and may include other conductive particles such as nickel, silver or graphite particles, carbon black or acetylene black) carried in a binder with a volatile carrier which will evaporate at room temperature. A hard conductive coating is formed after the volatile carrier has evaporated, which reduces the initial interior cell depolarizer/can interfacial resistance, and maintains it after storage at a lower level than that of uncoated cans. The coating composition is applied to the interior of the cans after they have been formed, by such steps as dipping, filling or spraying.

Description

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This inventlon relates to alkalirle cells, and particularly to containers or ca-thode cans into which alka]ine cells are assembled. This invention fincls its principal u~e in cylindrical alkaline dry cel~s which ~lave a substan~:;a:l axial lenyth as cornparec-l -to -their diarneter. ~uch cells bear the general designations, as to their size, ranying from "AAA" as the smallest up to "D" as the lar~est.

~ACI~GROUND OF_THE INVENTION.
One of the principal eauses for the 105s of apparent energy capaeity of alkaline dry eells, onee they have been manufactured and are placed in storaye such as shipping inventory or on merehants shelves for purehase by the consuming public, -- and indeed, abusive storage by the eonsumer sueh as in the heated interior of automobiles, and/or for long periods of -time -- has been the inerease of eontaet resistanee between the material of the cathode within the eell and the container in whieh the eell has been assembled. This inerease in contact resistanee may be manifested by a redueed on load terminal - voltaye, faster reduetion to a eut-off voltage, or redueed photoflash eapabilities. It oeeurs beeause of the faet that the - material of the eell eontainer or ean -- usually niekel plated steel -- -- is subjeet to eorrosion, partieularly in the presenee of alkaline eleetrolyte. of course, the eleetrolyte most often used in sueh eells is potassium hydroxide, whieh may have additional amounts of zine oxide admixed thereto.
one approaeh to overeome the problem of internal eorrosion apart from niekel platinc3, is to provide yet an :,` 1 ,: , ., ,~
.,, ~2~3~7 ditional conductive coating on the in-terior surface of the cari, which coating may then provi~le a low resistance interface bet~Jeen the cathode material an~l the can, whi:Le at the sarne tirne protecting the material of the can frorn corrosion.
The decision to provide an electrically conductive layer on the interior surface of the cathode can has prompted a review of the prior art, yenerally in respect of conductive coatings, and particularly for any art which may relate to the presence of a conductive coating on the interior surface of a cathode can, with the following results:
WHITBY et al in U.S. Patent 2,806,07~, issued September 10, 1957, teach a cylindrical dry cell battery in which the inner can wall and the adjacent anode surface are coated by a layer of electrically conductive "grease" -- which is a dimethyl siloxane filled with silica. This "grease" provides a contact between the anode and the can. However, so as to uniformly distribute the coating on the inner surface of the can, the can is subjected to radio frequency heating.
KILDUFF in United States Patent 3,751,3~1 issued August i, 1973, has provided a non-corrodible electrically conductive underlayer to a metal support body, which is sufficient to prevent the formation of an interfacial resistance barrier between the metal support body and a subsequently applied coating. This electrically conductive material is applied to the metal support body in admixture with a thermosetting resin. The thermosetting resin may be a water emulsifiable epoxy resin, and is admixed with a conductive material such as carbon or graphite.
After curing~ a second coating which consists of a mixture of lead dioxide and a thermosetting binder is applied, and the ., ~` 2 :..

., , ; ~tructure is therl suitable for uge as a reser~e batt:*~ electro~le in an acid system.
KUWA~I~KI el al :in United States patent 3,/~4,39~, :issued October 9, 1373, teach an inside-out primary dry cell in which the meiallic container is coated with a conduc-t:ive rnixture of thermoplastic resin and graphite or acetylene black. This celJ is saia to have yood performance characteristics, particularly when operating in a deep discharge mode to a high current load.
None of the above United States patents have, however, provided a suitable coatiny for the interior surface of alkaline cells, particularly where the coatiny must provide a high conductivity -- i.e., low resistance -- current path between the cathode material of the cell and the cell container, so as to establish a conducting circuit -through the cell; while, at khe same time, also providing a coating which will withstand the rigors of manufacturing steps where the assembly of a cell is ully automated and is accomplished at very high speeds such that any one assembly step may only take fractions of a second. Still further, it is not in the least desirable to use any conductive coating on the interior surface of a cathode can which would occupy any significant volume, thereby reducing the volume within the can which is available for active electrode or electrolyte material.
Japanese Patent Publication 4~3~1-19~3, published March 22, 1983 by SHI~ODA et al, teaches an alkaline dry ccll battery ` where the interior surface of the cathode can is coated with a -~ conductive coatiny which comprises polyvinyl isobutyl ether and ~`` carbon -- which rnay be graphite or flake shaped graphite, and/or ;
`~ acetylene black. However, SHINODA et al, while claiming to ~` 3 , :
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provide their con~uc-tive coatirlcJ on the interio~ surf~ce of -tne cathode can, whi.ch resul.ts in alka~ine cells ha~ing high short circuit currents even followirly storage of six to ~welve rnon-ths, have provided a coatincJ which is s-ticky to the touch, and which has rubber elasticity. I'his suggests, therefore, that the electrically conductive layer which i5 formecl on -the interior surface of the can, may also be relatively soft so that, when the cathode material is loaded in~o the can, especially where the cathode material is preformed extruded or cornpacted pellets or slugs, the coating on the interior surface of the can may be scraped off and thereby be of no significant value.
Because of that problem, SHI~ODA et al teach that their catllode is a blend of manganese dioxide powder and graphite, which is packed into the can. However, that requires a step which takes a significant amount of time during the manufacturing process, and which cannot ensure consistant and repeatable characteristics frorn cell to cell of a batch of many cells that are manufactured under high speed conditions. Moreover, SHINODA
et al require that a further manufacturing step be taken, by heating the container and thereby dissolving the material of the electrically conductive layer after the cathode blend has been incorporated i.nto the cell. This step is taken so as to fill the `uneven spaces on the inner wall of the container and thereby enhance the electrical contact between the container and the cathode blend.
The present invention, on the other hand, has none of ithe shortcomings of SHINODA et al. In particular, the present invention provides a coating composition which achieves essentially the same results -- that is, significantly reduced ~, 4 i . .

~63~7 ~. rosion of the steel can, which may be nickel plated as well and thereby increased short circ~it performance, with ~uch lower cathode/can interface voltage drop due to contact resistance at that interface. ~oreover, the present invention provides a coating composition, as well as a cell can or cathode container having a coatiny on its interior surface, where the coating is hard and not subject to scraping. rrhus, the coating will not lose its physical placement within the can and thereby its effectiveness after the cell has been assembled during 10 manufacturing;~ and, as well, the coating which results according to the present invention is substantially impervious to alkaline electrolyte, while being at the same time electrically conductive.
~` Thus, especially when the cell depolarizer or cathode is 15 placed into the can and is tightly fitted therein to -- such as by an interference fit -- the contact resistance between the can and the cell depolarizer may be initially in the range of from zero to twenty milliOhms when measured at room temperature, and after storage (even under extreme conditions of temperature) the ~ 20 contact resistance between the can and the cell depolarizer --`; cathode -- may increase only in the range of from zero to four times the initial resistance. klternative methods of placing the cell depolarizor in a can, apart from - pressing depolarizor pellets which are in interference fit with the can, but which ` 25 will ultimately result in the same characteriskics as discussed immediately above include placing loose fitting pellets into the ~` can and then recompacting them by placing a rod into the central , ~. .
, portion of the cathode pellets and then applying compacting pressure against the pellets so as to recompact them and spread , ~
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,, , ~Z~3~7 ~h~ compacted catilode materlal. ou~wardl~; or extrudirlg -tile cathode rnaterial around and pas-t a rod placed in the centre of the can, s.o as -to ensure that the lenyth o: -t'he can ~,/hich is intended to be filled wi~:h cat'hode or cell depolarizor materia].
is substantially colnp].etely :~illed wit~l that rnateria].; or other means where, in any event, a substantial~.y rig;.d Ina-t.~rial is placed into the can and, when placed, is tigh-tly fi-t-ted within the can.
Examples of ce]ls exhibitiny improved contact resistance characteristics as discussed above, and improved operatiny : characteristics such as higher shor-t circuit currents and better photoflash capacities, will be discussed hereafter.
It is a characteristic of the presen-t inven-tion that the hard coating, once formed on the interior surface of the cathode can, has substantially no tendency to swell in the presence of ~` alkaline electrolyte. Therefore, efficient employment of the interior volume capacity of the can may be achieved, having the most advantageous mix of volumes of the positive and negative ` electrode materia]s, liquid electrolyte, current collector, separator, and so on, while at the same time allowing for any . internal gassing or swelling of the separator, without having to :. otherwise accomrnodate swelling of the coating material.
` It has been found that the present invention also is !~ particularly useful in cell designs which accommodate tigh-tly ~. 25 fitted cathode pellets, that the can may have a plurality or i~ inwardly directed ridges which extend vertically for ~;' substantially the entire heiyht of the can, and which are spaced circumferentially around the can. Those ridges tend to secure the cathode or cell depolarizer within the can rnore efficiently, and ~i ';t ~. .
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at the same time provide ~or ~lrm cvn~ac~ ~etween the Ce11 depolarlzer and the can and t~lereby provide a good current path.
~t t~le same time, some voi~ volume ig perrnitted ~or occur~ation by electrolyte.
It is recogni~ed by the present inventior1 that the coating compositions that are particularly in-tencled for use in keeping with this invention demonstrate substantially no tensile strength. Therefore, it is a c~1aracteristic of -the present invention that the cell container or can is firs-t formed such as by being stamped or drawn Erom material such as nickel plated steel and thereafter the coating is applied to the interior surface of the formed can by applying coating composition and permitting it to cure, as discussed herea~ter.
It has been found, rather unex~ectedly, that certain colNnercially available carbon based lacquers which are said to be essentially semi-conductive, and are intended for uses entirely differently than the present purposes, are suitable for the purposes of the present invention. They include a product marketed by W.R. Grace & Co., in association with the trade rnark ECCOCOAT 257, and another product marketed by Acheson Indus-tries, Inc. in association with the trade mark ELECTRODAG l~9.
Generally, however, it can be said that the coating composition for use in the present invention is one which ineludes earbon partieles carried in a binder with a volatile ~5 earrier, where the earrier is such that it will evaporate a-t roorn temperature, where the binder is such as to form a hard coatin~
over a surface onto whi.ch it has been applied after the carrier has evaporated, and where the hard coating is substantially impervious to alkaline electrolyte and is electrically .~ ~

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conductive. The coating colnposition may also inc~ude, as a conductive component -t~lereof, n:ickel particles, silver particles, yraphite particles, carbon bl~ck, acetylene hlack, or ar,y or of them.
Moreover, the binder may be such a5 a nitrocellulose lacquer or other fortified oryanic polymer; and the coating composition may first be adrnixed with butyl ace-tate beEore it is applied, or it may include methyl ethyl ketone as a diluent.

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`~ 10 BRIEF DESCRIPTION OF THE D~AWINGS:
. The above features and advantages of the present invention are more fully described hereafter, and a typical preferred embodiment is illustrated in the accompanying drawinys, ~ in which:
:'' - 15 Figure 1 is an exemplary axial cross section of a ~` typical alkaline cell according to the present invention at a stage duriny its manufacture when the cell depolarizer has been inserted into the container; and .~
Figure 2 is an exemplary diametric cross section of a similar cell to that of Figure 1.

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ESCRIPTION OF_T~E_PREFERRED EMBODIMENTS:

As noted above, it is the principal purpose of this ~:, invention to provide a cathode container having a coatiny on at .~ ., ~ 25 least the major portion of its interior surface, whereby the ~ `
operatiny characteristics of the cell have experienced no ~`~-i significant deterioration following storaye, either at the time ~ .~
when the cell goes into the hands of the consumer who has purcbased it, or later. Storage may be as little as one or two .. 8 .... .
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i . `, ~Z~i3~7 weeks or as ~nuch as many mon-ths, and may occu~ at room temperature or at elevated or ~epressed temperatures, and occurs due to the necessity -to rnove cellg int.o the manufacturer's inventory, and then into t~le ~listribution channels, onto -the merchants' sllelves for purchase by the consurner, and in -the hands of the consumer. Significant periods o~ time may ~ass during all of those stages.
The presen-t invention also provides the steps for the method of preparing an alkaline cell, at least to the stage where at least a portion of the cell depolarizer is inserted into the cathode can of the cell.
Referrin~J to Figures 1 and 2, a typical but exemplary configuration is shown of a portion of a cell 10, which comprises a container or can 12 which may be forrned of such material as steel, and may be stamped or drawn from that material. The material of the can 12 may be plated with nickel or nickel alloy, at least on the interior surface thereof.
Over the interior surface of the can 12 there is a coating 14 which is in keeping with the present invention, and is - 20 described in more detail hereafter. Also within the cell 10 is a ` cell depolarizer 16 which may have an opening 18 in its centre for the insertion of the other electrode material, a curren-t collector, and so on. The preci.se details of -the assembly of the cell are not relevant to the present invention.
The can 12 may be forrned with a plurality of ridges 20, each of which extends vertically for substantially the entire height of the can, and the ridges are spaced circumferentially around the can. [For purposes of the present discussion, four ridges are shown, but there may be as few as three and as many as .`~
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~63~J~37 .welve or more.~ In a "o" si~e ce:L.l, the ri(~es may ~.ave an inwardly extendln~ height of about O.U32 inches.
As noted, the coatiny composition of the present invention has a carrier which wlll evaporate at room temperature.
When the volatile carrier has evapora-ted, a hard coati.ng remains, and that coa-ting has the general characteristic of a Matrix which remains and is firmly bonded to -the material of the can. T'ne conductive component of the coating composition is securely retained in place in the interstices of the matrix; so t'ha-t a contiguous, conductive, hard, coating is formed, which coating is substantially impervious to the alkaline electrolyte -- which may ' be po.assium hydroxide and may have zinc oxide admixed thereto --.. and which has no tendency to swell in the presence of the alkaline electrolyte.
~' 15 However, because the hard coating has no tensile `~ strength, it must be put in place after the container or can is ~' formed. I~hat may be accomplished, for exa~nple, by any of the ~ following steps:
x; (a) the can may be dipped into a bath of coating .~
~`l 20 composition and w.ithdrawn therefrom, so as to leave a residue of coating composition within the can;
`` (b) the can may be filled with coating composition and ~' then spilled, so as to leave a residue of the coating composition ~j within the can; or . 25 (c) the interior or the carl nlay be sprayed with the coating composition, and any residue may be permitted to run ou-t from the can.
`' Indeed, in certain circumstances, the interior of the i~, ~-~ can may be brushed with the coating composition.
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Thereafter, -the volatile 501verlt o.~ the coa~i,ny composition is permitte~ to evapora-te, such as a~ room temperature for at leas-t -three 'hours, or at an elevated temperature of 55 to ~0 C for a-t least ().2 to 2 hours.
~lternative me~:hods of applyirl(3 the coatiny composition to the interior of the can include preheating t'he coating composition to 25 to 45 C, and spraying it in-to the can. In yet ~ another coatiny method, the cans themselves may be preheated -to : between 50 and 150 C, with the coating cornposition being between and 45 C. The coatiny composition is then sprayed into the : cans, which are then air dried at room temperature for at least 15 seconds. During that period o~ time, the volatile solvent is driven off, and the can cool-s down at least to some extent.
The initial contact resistance between the can and the cell depolarizer 16, may be measured and may be ~ound to be initially in the range of zero (that is, below the measurernent sensitivity of the instrument being used) up to about 20 ; milliohrns -- usually in the ranye less than 4 milliOhrns. Then, followiny storaye under various conditions, such as frorn two ~ 20 weeks to fifty-two weeks at room temperature, two weeks at 55 C, '~ or one week at 71 C, tests have shown th,at the contact resistance between the can and the cell depolarizer rnay have ~ increased only in the range of frorn zero -~ that is, not at all ~ -- to four times the initial resistance when the cell was first i 25 formed. Thus, even after storage under adverse conditions, the ,'~ contact resistance between the can and the cell depolarizer may '' be in the range of frorn substantially zero up to ~0 milliOhms at `, the worst. Similar uncoated cans -- but haviny a nickel plating ,', on their interior surface -- have been tested under similar ~ `
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` nditions using identical testiny e~uiE~Irlent, afte~ thFy were stored in exactly the sarne conditions, and have demonstrated increases in contact resistance on storage up to 200 milliOhms or more.
The thickness of the hard coating, once it has been placed and cured, may be as little as 0.000~ to 0.()03 inches, typically 0.0004 to 0.001 inches. Such thin coatings have no significant effect on the decrease of the internal volume of the can; and since the coating shows no tendency to swell in the 10 presence of alkaline electrolyte, there is no necessity for permitting addltional volume within the container to accommodate such swelling. This permits the addition of more active material to the cell, thereby giving it longel life and even better storage characteristics.
The coating composition may be admixed with butyl acetate over a range of ratios of composition to butyl acetate of from 1:8 to 8:1. The choice of the mixing ratio depends on such characteristics as the initial characteristics of the coating composition as it has been manufactured or purchased, the speed 20 of the manufacturing line and the method in which the coating composition will be applied to the interior surfaces of the cans, the temperature and rate at which the coating composition will be cured, and the size of the cell container (large or small).
Representative test results have demonstrated the 25 following:
In one series of tests, control (i.e., uncoated) cells stored for six weeks at room temperature have shown an average increase in internal cathode/can contact resistance of 40 ` milliOhms, which would result in a loss of 16 millivolts of :~ .

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.erminal vol-ta~e at a cel:L cur~erl~ :int-J a :r~ ti.ve:ly he-l~Jy loa(l of 400 milli~mps. Coated cells, according to the present inven-tion, and stored under t~le sarne concll-tions, showed an averaye increase of illternal resistance of zero, and therefore no measurable loss in -terrninal voltat~e o.~ -the cell even into a '~0() . milliAmp load.
Likewise, control cells stored or -two weeks at 55C
showed an average increase of internal resi.stance of 85 milliohms, for a loss of terminal voltage of 34 rnillivolts into a 400 milliAmp load; whereas cells having an internal coating according to the present invention, and stored under the same conditions, showed an average increase in internal resis-tance of 4 milliohrns for a loss of.terminal voltage of 1.~ millivolts into : a 400 milliAmp load.
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15Other cells in sizes ranging frorn "~" to "D", following storage for two weeks at 55C, showed irnprovements in ; operating characteristics of c~utoff voltage into various loads of ``'3Up to 22~. Moreover, "AA" cells into a photoflash load showed improvements of 20~ in terms of the number of flashes permitted, 20 and 50~ recovery time after the fifth flash, as compared to control cells.
;The short circuit current of various cells were tested following differiny storage conditions, against control cells.
For example, test "D" cells showed no signif:Lcant change o:E
~5 average short circuit current for cells according ~o this .
`~invention, after various storage conditions; so that cells .~stored at 55 G C for two weeks, and an average short circuit current of 19.3 milliAmps, and cells stored at 71 C for one week had an average short circuit current of 19.4 milliAmps. Control . ,. ~ .
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3~7 'D" cells sllowed a decrease of average srlort circuit current to 14.~ milliArnps for cells ~store(i at 55' r for two weeks, and to 11.~ milliArnps for cells stored at 71' ~ for one week. "r" cells showed an average short circui~ currerlt of 1~.~ milliAmps for cells s-tored at 55'~ for -two weeks; w~ereas the control cells dropped froM 9.9 milliArnps initially to 8.3 milliArnps followiny storage. Substantially similiar results were obtained with "AA"
cells.
The benefits of a hard coating which is impervious to alkaline electrolyte, and which improves -the internal contact resistance of alkaline cells, have been fully discussed and clearly demonstrated by the above. The fact that the coating is a hard coating, precludes the possibility that the coating will be scraped in any substantial amounts into the bottom of the cell container when the cell depolarizer is inserted into it; and it also provides for much easier can storage where the cans may be stored in bulk containers without having to worry about the possibility of the coating on the inside of the cans drooping or running during storage. Various specific exarnples of coating composition have been provided, but it is shown that in all events the coating composition includes at least carbon particles and may include additional conductive particles, carried in a binder with a volatile carrier which will evaporate at room temperature.
In general, yiven that the contents of an alkaline cell -- that is, the arnount of cathode material, anode material, electrolyte, the separators, and the cell construction including the can material, the seal, and the rnethod of the cell construction -- are constant between cells according to this ~2Çi36~7 invention and control cells or c-:elLs that are ~>resent]~
available, with tile only di~ference being t~le addition of the coating composit:ion and tlle presence oE t~le harc-l coatiny on the interior surfaee oE -the cathode eontainer in keepiny with this inven-tion, if follows !ha-t Eor the most par~ the -total capaeity in rnilli~np-hours oE ee:Lls aecorcling to this invention and ordinary cells is essentially the same. ~Iowever, cells according to this inven-tion have shown a hiyher initial eurrent, higher terminal voltage on load, with a hiyher short eireuit eurrent.
The eells provide a higher average eurrent into a eonstant resistanee, althouyh perhaps for a slightly shor-ter period of time due to the maximum milliAmp hour capaeity of the eell; but they provide better serviee hours for eells workinc3 into a eonstant eurrent load, and a mueh shorter reeharge time for cells operatiny with a photoflash load.
~ everal examples of eell testiny have been describecd and diseussed, and a typieal eonstruetion whieh is exemplary and not intended to limit the present invention, has been indieated. The seope of the present invention is defined by the appended elaims.

Claims (20)

CLAIMS:

1. For use in alkaline cells, a cathode container having a coating on at least the major portion of the interior surface thereof;
where the coating composition for said coating includes carbon particles carried in a binder with a volatile carrier;
where said carrier is such that it will evaporate at room temperature;
where said binder and carbon particles are such as to form a hard conductive coating over the surface onto which said coating composition has been applied, after said carrier has evaporated;
and where said hard coating is substantially impervious to alkaline electrolyte, and is electrically conductive;
whereby the contact resistance between said can and a cell depolarizer when tightly fitted thereinto is initially in the range of zero to 20 milliOhms when measured at room temperature, and after storage of at least one week said contact resistance increases only in the range of zero to four times the initial resistance.

2. The interior coated cathode container of claim 1, where said hard coating has substantially no tendency to swell in the presence of alkaline electrolyte.

3. The combination of claim 2, where the electrolyte is chosen from the group comprising potassium hydroxide and admixtures thereof with zinc oxide.

4. The interior coated cathode container of claim 2, where the can has a plurality of inwardly directed ridges which extend vertically for substantially the entire height of the can, and which are spaced circumferentially around the can.

5. The interior coated cathode container of claim 1, where said binder is a nitrocellulose lacquer.

6. The interior coated cathode container of claim 1, where said coating composition has first been admixed with butylacetate.

7. The interior coated cathode container of claim 1, where said coating composition is a commercial composition sold as ECCOCOAT ?257.

8. The interior coated cathode container of claim 1, where said coating composition is a commercial composition sold as ELECTRODAG ? 109.

9. The combination of claim 4, where the cell depolarizer in interference fit with at least the inside facing surfaces of said inwardly directed ridges.

10. The interior coated cathode container of claim 1, where said coating composition further includes, as a conductive component thereof, at least one of the group comprising nickel particles, silver particles, graphite particles, carbon black, and acetylene black.

11. The interior coated cathode container of claim 1, where said coating composition includes methyl ethyl ketone as a diluent.

12. The combination of claim 1, where said container has a first coating or plating of nickel or nickel alloy on at least the interior surface thereof before said coating composition has been applied thereto.

13. A method of preparing an alkaline cell, at least to the stage where at least a portion of the cell depolarizer is inserted into a formed can with a coating composition which includes carbon particles carried in a binder with a volatile carrier;
permitting the volatile carrier to evaporate so as to leave a hard, conductive coating on the inside surface of said can, which coating is substantially impervious to alkaline electrolyte; and placing into said can at least a portion of the cell depolarizer, so that, when placed, said at least a portion of said cell depolarizer is tightly fitted into said can.

14. The method of claim 13, where the coating composition is applied to at least the inside surface of the can by one of the following steps:
(a) dipping the can into a bath of coating composition and withdrawing it from the bath so as to leave a residue within the can;
(b) filling the can coating composition and then spilling coating composition from the can so as to leave a residue within the can;
(c) spraying the interior of the can with coating composition at room temperature; or (d) spraying the interior of the can with coating composition which has been pre-heated to 25 to 45° C.

15. The method of claim 14, followed by one of the following steps:
(e) allowing the volatile solvent to evaporate at room temperature for at least three hours; or (f) allowing the volatile solvent to evaporate at a temperature of 50 - 90° C for at least 0.2 to 2 hours.

16. The method of claim 15, where said coating composition is admixed with butyl acetate in the range of composition:butyl acetate ratios of from 1:8 to 8:1.

17. The method of claim 13, where said coating composition further includes, as a conductive component thereof, at least one of the group comprising nickel particles, silver particles, graphite particles, carbon black and acetylene black.

18. The method of claim 13, where said coating composition includes methyl ethyl ketone as a diluent.

19 The method of claim 13, where said formed can has a first coating or plating of nickel or nickel alloy on at least the interior surface thereof before said coating composition is applied.

20. The method of claim 14, where the coating composition is applied to the inside surface of the can when the can has first been pre-heated to a temperature of between 50 to 150° C;
where the coating is sprayed into the can at a temperature of between 15 to 45° C; and where the can is then allowed to air dry at room temperature for at least 15 seconds.