CA1287872C

CA1287872C - Secondary battery

Info

Publication number: CA1287872C
Application number: CA000555042A
Authority: CA
Inventors: Sanford A. Siegel; Stephen A. Noding
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1986-12-23
Filing date: 1987-12-22
Publication date: 1991-08-20
Anticipated expiration: 2008-08-20
Also published as: EP0294472A4; KR890700271A; JPH01501666A; KR910009390B1; US4714665A; EP0294472A1; WO1988004834A1

Abstract

ABSTRACT

This invention relates to a secondary battery comprised of three polymer films, the third containing an electrolyte and the first and second containing an electrochemical species which may be in an anodic or a cathodic state depending upon whether the battery is discharging or is being recharged. The third polymer sheet is substantially not electrically conductive under battery discharge voltages, but is electrically conductive under battery recharge voltages. The first and second sheets are electrically conductive under both the discharge and recharge voltages. In a preferred form, the electrolyte and the electrochemical species are uniformly distributed within their respective films by dissolving the electrolyte and the species in a plasticizer which is incorporated within the polymer films.

Description

37~
, SECONDARY BATTERY

Thi~ invention relate~ to a secondary battery compri~ed of film ~heets or film~ o~ a polymeric ; material. One sheet containq an electrolyte and the other two ~h~ets contain electrochemical specie3 which : may be in an anodic or a c~thodic ~tate dependîng upon whether the battery i~ di~charging or i~ being chargedO
A ~econdary battery i~ most ~imply de~ined as a battery which can be recharged. This recharge capability is due to the incorporation~ within the battery 7 of ~lectrochemical reactants whioh undergo a highly reversible electrochemical reaction to convert chemical energy to electrical energy upon di~charge o~
thc battery. Recharging of the battery converts electrical energy to chemical energy. The eleotrochemical reactants can be identiPied a~
electrochemical ~pecie~ having either an anodic or cathodic ~tate depending upon whether the battery is in the di~charge or the recharge mode. The anodic state i~ identi~ied with the oxidation hal~ of the electrochemical reaction, while the cathodic state is identified with the reduction half of the 2~ electrochemical reaction.

34,228-F -1-'. ' ' '- "' ' ": ,, ' ' '' . . ~

During the di~charge mode9 the battery acts as a voltage device in which the di~erence in the electrochemical potential between its anodic electro-chemical qpeoie~ and it~ cathodic electrochemical specie~ ~erv~s as a driving force ko ~upply electrons through a load connected to the batteryO The electrons produced by oxidation o~ the anodic electrochemical ~pecie~ pas3 from the positive electrode, through the load and on to the negative electrode of the battery~
1~ The negative electrode is ln a~ociation with the cathodic electrochemical ~pecies. The acceptance of el~ctron~ by the negative electrode results in a reduction o~ the cathodic electrochemical speciesO
When the potential di~arence between the electrode~ of the battery approaches zero volts, the source of electrons is ~ubstantially exhau~ted and the battery needs to be recharged.

During the recharge mode, the battery behaves as an electrolysis device in which electrical energy i3 applied to the battery to provide the necessary electron~ to oonvert the applied electrioal energy into ~tored ehemiaal energy. The electrochemical ~pecie~, which was anodic and ~erved a~ a source o~ elec~ronq during discharge, becomes cathodic during recharge and accept~ electron~. The ele¢trochemical ~pecies which wa~ cathodic during di~charge becomes anodic during recharge. Although the role~ o~ the electrodes, i.e 3 the acceptance or the discharge of electrons, depends upon whether the battery is in the recharge or di~charge mode, the poqitive electrode is always connected to the positive lead of the load. Similarly9 the negative electrode is alway~ connected to the negative lead~

34,228-F -2~

:' Common ~secondary ba~teries are the alkaline and lead-acid batteries. These two types oP batteries usually provide rigid cases in which the electro-chemical species are con'cained. Due to the requirements of the materials of construction, these batteries can have considerable thicknesses and weights. This is especially true of the lead-acid battery.
In an attempt to reduce the dimensions of secondary batteries, recent battery research has turned to the use of poymeric films in secondary batteries.
The use of such polymeric film~ can provide batteries having very thi,n cross-sections and decreased weight.
It i3 therefore an object of this invention to provide a novel secondary battery which incorporates the utili~ation of polymeric film and which, as a result/
has a very thin cross-sec~ion even when constructed of a plurality of cells. It is also an object, of this invention to provide a secondary battery which has substantial flexibility.
More speoifically, the invention resides in a secondary battery which comprises-(a) an ionically and and electronicallyconductive fir,~t polymer film having substantially uniformly distributed therewithin a reactive electro-chemical species which contributes to the ionic conductivity of said first polymer film and which is electrochemically reduced when said battery is being discharged and electrochemically oxldized when said battery is being charged, 34,228-F -3-, ..;
., .,~.~ . .

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(b) an ionically and electronically conductive qecond polymer ~ilm having substantially uniformly distributed therewithin a reactive electrochemical .qpecies which contributes to the ionic conductivity o~ ~aid 3econd polymer film and which i~
electrochemically oxidized when said battery is being di~charged and electrochemically reduced when said battery i being charged 9 (c) an ionically conductive third polymer film in contact with said ~ir~t and second films, said third film eomprising~
(i) a polymer 9 (ii) a plasticizer ~or said polymer, and (iii) an electrolyte for said battery which i~ disas~ociatingly solubilized in said pla~ticizer~ said plasticizer and the ~olubilized electrolyte being ~ub~tantially uniformly di~tributed within ~aid polymer, ~aid third Pilm being ~ubstantially electronically nonconductive under di~charging voltages and electronically conductive undsr charging voltage~, and (d) a ~ir~t electronically conductive collector in contact wlth said Pir~t polymer ~ilm and a second electronically conductive collector in conta~t with ~aid second polymer film~
For the purposes of thi~ invention, the electron conduction of the two ionically conductive ~ilm~ should be greater than 10 5 (ohm-cm~~1. The third polymer film i3 e~sentially ele~tronicall~ non-conductive under t~e discharge voltage, but is electronically conductive under its rechar~e voltage~

34,228-~ -4-,.

This nonconductance is generally below 10 ~(ohm-cm)~l.
The third polymer film is al90 ionically conductive.
One o.~ the two electronically conductive polymer films contains an electrochemical species which is reduced when the battery is being discharged and oxidized when the battery is being charged~ The other electronically conductive polymer fil~ contains an electrochemical specie~ which is oxidized when 'che battery i~ being discharged and reduced when the battery is being chargedO Both electrochemical specie3 contribute to the ionic conductance o~ these two ~ilmsO
To ~acilitate the collection of the electrons produoed by the battery during di3charge and the application Q~ a recharge voltage to the electronically conductive polymer films during recharge9 it i~
preferred that the secondary battery o~ thi~ in~ention additionally include two electronically conductive collectors. These collectors are generally made o~
graphite, pla~ti¢~graphite compo~ite , carbon cloth~ or metal. If the collectors are made of metal, they are preferably of the same metal to avoid electrolyti¢
interaction between the collector~. Metal csllector~
are pre~erably made of aluminum, copper, bra3~, platinum, ~ilver, gold, or alloys of th0se metals. So that the ~econdary battery o~ this invention can have maximurn ~lexibility, the~P collector~ are preferably provided a~ metal foils. The collectors can also be provided as pla~es, coatings, or ~ilm~ which are applied to the ou~8r surfaces of the two electronically conductive polymer films by vacuum or electro deposition.
~5 34,228-F -5-,, , - . ,. . ~ , . . .

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78~7 In a pre~erred ~orm, the secondary battery of thi invention i~ in the form o~ a laminate o~ the above-mentioned polymer film~ and oollectors. This laminate i~ constructed so that the third polymer ~ilm is positioned between the two electrically conductive polymer ~ilms~ Laminated to or deposited on the outside surfaces o~ the electronically conductive polymer ~ilm~ are the collectors. The resultant laminate can be held together mechanically or by adhesion. The adhesion can bs provided by the lamina themselve3 or by an adhesiveO The use of an adhesive requires that the adhesive be selected so that its electron and ionic conductivity does not interfere with the operation o~ the ~econdary batteryO
It is preferr~d that the two electronically conductive ~ilm~ each compri~e a polymer, an agent to render the polymer electronically conductive, a plasticizer ~or the polymer, and 9 aa an anodic/cathodic electrochemical 3pecies~ a ~alt disassociatinely solubilized in the pla~ticizerO
For most polymer film~, it is necessary to use an agent ~or rendering them eleotronically conductive.
The agent can be applied to oppo~ike surfaces o~ the ~ilm as a coating or by doping the polymer ~ilm or incorporating therewithin graphite~ finely divided carbon or other eleotronically conductive sp0cies.
Doping o~ and the introduction of graphite, carbon, etc., into polymer films i~ well known in the art and the principle~ of ~uch are applicable in the instant case.
The salt u~ed in one of the polymer films has the formula MXa, while the salt u~ed in the other 34,228-F -6-. ', ' ' -- '~

polymer film has the formula M~Xbo To provlde the needed electromotive force between these two polymer films, the M' or the Xb constituent of the M'Xb ~alt has an electrode potential less than Mo Both M and M' are cation~ while X i3 an anion and a and b are the oxidation number~ of M or M~o The cations M and M' preferably have a Pauling'~ electronegativity le~3 than that of the anion X by at least 0O3 units~ Generally, suoh differenee~ in electronegativitie~ protend ~uitable ~olubilitie~ of the salt in the plasticizer con~tituent of the polymer ~ilm~ Pre~erred MXa and M'Xb salts are tho~e in which M and M~ are independently selected from alkali metal ions9 alkaline earth metal ion~, zinc ion~ copper ion9 mercury ion, and ~ilver ion9 and in which X is a halogen, e~g., Cl-and I- or an organic radical, eOg. 9 (C2H302)-.
Especially useful MXa and M'Xb salt~ are CaI29 ZnCl2, CaCl29 CuCl2~ Zn(~2H3o2)27 BaI2, LiI 9 and ZnI2O The mo~t preferred pairings of MXa and M'Xb are CaI2 and CaI2, CuCl2 and ZnCl29 LiI and ZnCl2.
It i~ de~irable to maximize the amount of ~alt which can be uniformly distributed within the polymer film. The maximlzation of the ~alt concentration is dependent upon the ~olubility of the salt in the pla~ticizer and upon the amount of pla~ticizer which can be used with the polymer without deleteriou~ly a~fecting the latter'~ propertie3 Salt concentrations 3 in the plasticizer within the range of ~rom 5 percent to 30 percent of total ~alt saturation are deemed adequate to excellsnt for the purposes of this invention. ~eside~ the plasticizer being a good salt ~olvent, it has to al~o maintain its pla~ticizing function. It i~ preferred that the plastlcizer be 34,228-F -7-, ' .

7~37~:
--8 ~

highly compatible wikh and be able to maintain a continuou~ phase throughout the polymerO ~ :
Pre~erred plasticizers which exhibit good solubility for the salts of this invention and which maintain ~heir plasticizer ~unction are exemplified by alkyl ether esters o~ benzoic acid9 terephthalic acid9 phthalic acid 7 and adipic acidO The most highly preferred plasticizer is an ether ester of terephthalic acid having the ~ormula:
T2 1I fi T2 .
R1~0CHCH2)yO C ~ C-0-(CH2CH~)xR1 wherein R1 i~ a phenyl radical or aliphatic hydrocarbon radical of the formula CnHm wherein n i~ an integer o~
1 through 8 inclusive ~nd m is equal to 2n~1; R~ i~
either hydrogen or a methyl radical; x i.~ 2, 3, or 4;
and y i~ 2, 3, or 4. As a general rule, x and y will be equal. Satisfaetory results are obtained9 however, irrespective o~ whether x equal~ y. The most preferred of such ether e~ter~ is di(triethylene glycol butyl ether)terephthalate. When this parti¢ular ether ester i~ utilized, it i~ preferably pre~ent in eaoh o.~ the electronically ~onductive polymer ~ilm~ in an amount of from 5 to 50 weight percent ba~ed upon the total weight of the polymer, the plasticizer, and the salt in the film. These ether e3ters may be prepared in accordanee with the procedure disclo~ed in V~S. Patent No. 4,6209026.
Preferred salt/pla~ticizer combination~ are those in which the salt i9 ZnCl2, CaI29 CuCl2, or LiI

34,228-F -8-.

' 37~

~ g ~

and the plasticizer i~ di(triethylene glycol butylether)terephthalate~
The third polymer film ~ompri~es a polymer~ a pla~ticizer for the polymer 7 and an eleotrolyte for the battery. The electrolyte i~ di~a~ociatingly solubilized in the plasticizer. Thus, when the pla~ticizer is blended into the pol~mer to provide a homogeneou~ blend9 khe solubilized electrolyte i9 likewise uniformly distributed within the polymer. The electrolyte provide~ ionic and electron oonductivity~
the latter being at recharge voltages. The electrolyte can be any conventional electrolyte which i~ soluble in the pla~ticizer constituent of the third film ~nd which doe not deleteriously a~fect the film propertieY or the plaqticizing function o~ the plasticizer.
E~pecially quitable electrolytes are alkali metal tetraphenylborates and thiocyanate~. Most preferred of these are ~odium tetraphenylborate and lithium and 30dium thiocyanate. Since these eleetrolyte~ are 3alt~, their conoentrations in the third polymer film should not be so high that th~ ~ilm is rendered electronically conductive under the di~charge voltage of the battery. For example, it ha~ been found that when ~odium tetraphenylborat~ 1~ the electrolyte, di(triethylene glycol butylether)terephthalate i~ the pla~ticizer, poly(vinyl chloride) is the polymer, and the film has a thickne~ o~ from 0~05 to 0.5 mm, the 3 ~odium tetraphenylborate i~ pre~erably pre ent in an amount of about 1 weight percent based upon the ~otal weight of the polymer ~ilm. Sodium tetraphenylborate amounts above about 7 weight pereent generally render the third polymer film ~o electronically conductive that a ~hort will o~cur between the electronically 34,228-~ -9-7~7~

conductive polymer films 7 thus rendering the 3econdary battery of little use.
The pla~ticizer utilized in the third ~ilm may be any one o~ the plastici~.er~ hereinabove described ~or the two ele~tronically conductive film~ The same criteria are applied in selecting the pre~erred plasticizer ~or the third film as were applied for the two electronically conductive film~t i~e.9 the plastici2er mu~t exhibit good ~olubility for the particular ~alt to be dis~olved therein and must maintain it~ plasticizer ~unction with re~pect to the polymer within which it is incorporated. As is the case for the two eleotronically conductive films9 the preferred plasticizer ~or the third film is di(triethylene glycol butyl ether)terephthalateO In this instance, the amount of plasticizer u~ed ~hould be within the range o~ Prom 5 to 40 weight percent based upon the total weight o~ the polymer, the pla3ticizer~
and the electrolyte in the ~ilm.
The polymer constituent of the three films can be any polymer which can be formed into a film and whioh doe~ not deleteriously a~fect the functioning of the electrochemical ~pecie~ and the eleotrolyte and their uniform distribution throughout the polymer film.
Suitable polymer~ are poly(vinyl chloride), polyurethane, polystyrene t chlorinated polyethylene, poly(vinylidene chloride), and poly(ethylene terephthalate). Both yoly(vinyl chloride) and polyurethane are more preferred. Polyurethane is especially pre~erred a~ it possesses adhesive qualities which will allow it ko make good ~lectrical contact with the collector~. The ~ilms have a thickness of from 0.05 to 0.5 mm. Thinner ~ilm~, iOe., films having 34,228-F -10-- ,.
,: . , .
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a thickne~ of ~rom 0.025 to 2.5 micron~ are preferred ince they ars more condueive to electronic and ionic conductivity. Furtherg a thinner film allow~ ~or the construction of multicell batteries having a total thickness which iq still sufficiently small so that ~lexibility o~ the battery is provided.
The three films may each additionally contain various art-recognized stabilizerq and proces~ing aids.
For example9 epoxidized vegetable oil9 ~uch a~
epoxidized soybean oil, may be incorporated into the polymer formulation as a stabili~er. Solvent 9 quch as dimethylformamide 9 tetrahydro~uran, and dipropylene glycol methyl ether acetate, may be u~ed when ; 15 manufacturing the iilm~ of this invention by the ~olvent ca~ting method. When other method~ oP ~ilm formation are u~ed, other applieable conventional processing aid~ may be u3ed ~o long a~ ~uch do not interfere with the functions de~cribed ~or the three films of thi~ invention.
: The ~ilms of thi~ invention are generally produced in a conventional manner, however, it i~
2~ important that the MXa, M'Xb, and ele~trolyte salt~ be added to the pla~ticizer and not vice ver~a. By adding the ~alt to the pla~ticizer, higher ~olubilitie~ ~or the salt can be obtained and the formation o~ salt aggregate~ i~ avoided and thus, the MXa, M'Xb ~alts and the electrolyte Yalt are ~ubstantially uni~ormly di~tributed within their re~pective films. I~ has been ~ound that i~ the pla~tieizer is added to the salt, the result~nt ~olution give~ poor per~ormance when incorporated into the polymer film~ o~ this invention.

34,228-F

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~12-These and other features of khi~ invention contributing to ~atiqfaction in use and economy in manu~acture will be more fully under~tood ~rom the following description of a pre~erred embodiment o~ the invention when taken in connection with the accompanying drawings in which identical numerals refer to identical parts and in which Figure 1 is a side elevational view o~ a secondary battery of thiq invention9 and ~ Figure 2 is a sectional view taken through section lire~ 2 2 in Figure 1q Re~erring now to Figures 1 and 2~ th~re can be seen a ~econdary battery o~ this invention, generally designated by the numeral 10, comprising a laminate of three polymer films 12, 14, and 15 and two collector plates 18 and 20. As can be seen in Figure 29 intermediate film 12 i~ positioned between outer ~ilm~
14 and 16 whi~h are positioned, in turn, betwe~n collector plates 18 and 20.
Intermediate ~ilm 12 i~ ionically condu¢tive7 but electronlcally nonconductive at the battery discharge voltage and is eleotronically conductive at the battery recharge voltage. Intermediate film 12 contains a substantially uniform distribution of an electrolyte whioh has been solubilized in a plastlcizer.
Outer ~ilms 14 and 16 are ioniaally and electronically conductive at both di~charge and recharge voltages. Thi~ electronic conductivity can be achieved by incorporating within the outer films 14 a~d 12 electronically conductive ~pecies such as graphite or carbon. Outer film 14 contains a substantially 3~,228-F -12-.
' - ~ :. . - ' ' ' -~ -.

~13-uni~orm di~tribution of an electrochemical species which is anodic in character when the battery i~ being di~charged and i~ cathodic in character when the battery i~ being rechargedO Outer film 16 contain~ a ~ubstantially uniform di~tribution of an electrochemiaal species which i~ cathodic in character when the battery i~ being discharged and is anodic in character when the battery is being rechargedO The uniform distribution of these eleotrochemical species within the outer film~ 14 and 16 i~ achieved by dissolving the electrochemical species in a plasticizer which in turn is incorporated into the ~ilms~ The compo~ition o~ films 14 and 16 is in accordance with the prior di~cu~3ed compo~itions of the electronically conductive polymer films.
The battery includes two metallic collector plate~ 18 and 20 which are preferably made of ths ~ame metal and more preferably of a metal foil ~o that the battery will be ~lexible. The flexibility of the battery preferably approaches the same ~lexibility posse~ed by polymer films having a thickne~s equal to the thickne~s of the battery~
For the battery ~hown in the drawings, it oan be ~een that all of the laminae are coextensive with one another. Attached to point~ on the outer surface3 of the collector~ 18 and 20 are, re~pectively, wire lead~ 24 and 22. These two wire lead~ may be connected to the colleotor~ by any conventional means. For the embodiment shown in the drawings, the lead3 are eonnected to the collector~ by means of solder welds 23 and 25.

34,228-F -13-,' ~,' ' ' . ' .. . . . . . . .
:

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To a~sure high ~idelity in performance, it is necessary that the various laminae of the battery be urged into intimate contact with one another. For the embodiment shown in the drawings, this intimate contact is achieved by inserting the battery within an envelope 30 of a heat shrinkable material at ambient temperature. When the envelope 30 i heated to a temperature of from 70 to 100G, it contracts or shrinks and thereby urges the laminae into intimate contact ~ with one another. Heating for a period of about 5 minutes is suf~icient. I~ the battery is very thin 9 pre~sure may be applied to the envelopeJbattery combination during heating to prevent warping Other methods for ensuring intimate conkact between the laminae include the utilization o~ adhesives and pres~ure ko bind the laminae together or the u~e o~ a ~rame to mechanically urge the laminae into intimate contactO
It ~hould be noted that Figures 1 and 2 are not to qcale with respect to one another. So that the variou~ laminae can be distinctly seen 9 the cros~-qectional view 3hown by Figure 2 ha3 been expanded widthwi~e. In aotuality, the thicknes~ of the battery is much le~s than illu~trated and more in accordance with the relatively thin films and collector plates actually u~ed.
A feature of the battery of this invention i~
that elevated temperatures are not required to achieve u~eful discharge voltage~ ? but rather that the subject batteries can be conveniently di~charged and recharged at ambient temperatures, i e. 25C. An increase in temperature does, however, a~eot the mobility of the electron~ and increases the current outflow to thereby 34,228-F -14--.
.

~ ~ ~ 7 ~horten the time in which the electrons are removed ~rom the batteryO A temperature below ambient adver~ely affect~ the mobility of the elcctrons and decreases the current out~lowO The application of pressure to the battery components facilitate~ urface contact between the component~ of th~ battery and therefore also improves current removal since a greater sur~ace area is in contact so that a greater portion of the battery is active. The Yollowing batteries were ~ con~tructed and tested over at least 10 charge and discharge cycle30 A fir t electronically conductive polymer film was prepared as ~ollows:
A 25 weight percent lithium iodide solution wa~
prepared by adding lithium iodide to di(triethylene glycol butyl ether)terephthalate.
One hundred parts by weight of dispersion grade poly(vinyl chloride) wa~ added to 20 parts by weight epoxidized soybean oil and 33 parts by weight dipropylene glycol methyl ether acetate ~olvent with mixing. After a ~ub~tantially homogeneous mix was obtained, 105 parts by weight o~ 1 micron particle size graphite powder was added thereto with mixing. Then, to this mix was added the di(triethylane glycol butyl 3 ether)terephthalate 25 weight percent lithium iodide solution with ~urther mixing~ The re~ulting mixture was poured onto a smooth glass plate and a l'doctor blade" wa3 used to produce a film ha~ing a thicknes~ of about 0,38 mmO ~he film was cured in an air blown ovan for 15 to 20 minutes at a temperature o~ about 125C.

34,228-F -15- ;

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A second eleetronically conductive film wa3 prepared in the same manner a~ wa~ the first, except that 7 in~tead of lithium ohloride, zinc chloride was used, An ionically conductive film was prepared by ~he ~ollowing procedure. A 1 weight percent solu~ion o~ di(~riethylene glycol butyl ether~terephthalate sodium tetraphenylborate was prepared by adding the borate ~alt to di(triethylene glycol butyl ether)~
terephthalate at an elevated temperature (30C) and stirring J
Under mixing, 100 parts by weight o~ a di~peFsion ~rade poly(vinyl chloride) was added to 20 parts by weight epoxidized soyb~an oil and 33 parts by weight dipropylene glycol methyl ether acetate~ A
homogeneous mix wa~ obtained~ To this mixture~ the di(triethylene glycol butyl ether)terephthalate 1 weight psrcent sodium tetraphenylborate solution was added with mixing. Thi~ mixture wa~ then poured onto a ~mooth gla~ plate and reduced to a thicknes~ of about O.38 mm with a "doctor bladeO" The ~ilm wa~ cured in an air blown oven ~or 15 to 20 minute~ at a temperature of about 125C.
A battery was then formed oonsi~ting of a ~ir~t, generally 3quare bras~ plate having a surface area of 58 cm~ and a thickne~s of about 0~05 mm;
coextensive layers of the fir~t electronically conductive polymer; the ionically conduct.ive polymer;
the ~econd electronically conductive polymer; and a ~econd brass plate of the ~ame dimension as the first bra~s plate. The laminae were then mechanically pre sed together between two plates of a nonconductive 34,228-F -16-.- ~ . .
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.
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material, e.g., Plexiglass , a thermoplasti¢ poly(methyl methacrylate)-type polymer. An anode lead was connected to the first brass plate and a cathode lead was connected to the second brass plate.

A constant 400 mA, variable DC voltage charging current was applied to the cathode. The voltage varied from 2 to 100 volts and was varied to maintain the constant 400 mA value during charging. The initial charge period was 8 hours. Subsequent charge periods took only about 5 hours. The charged battery was discharged through a 10,000 ohm resistor. The discharge voltage was 1.5 volts, the discharge amperage was 2G0 microamps and the discharge time was 8 hours.
Example 2 The same procedure of Example 1 was followed, except that aluminum plates were used instead of brass plates. The resultant charged battery was discharged through a 10,000 ohm resistor and the discharge voltage was 1.5 volts and the discharge current was 200 microamps. The discharge time was 8 hours. Thus, no difference was seen between using brass or alumlnum plate3.

Example 3 The same procedure of Example 1 was ~ollowed, except that instead of di(triethylene glycol butyl ether)Serephthalate 25 weight percent calcium iodide solution was substituted for both the di(triethylene glycol butyl ether(terephthalate 25 weight percent lithium iodide solution and the di(triethylene glycol butyl ether)terephthalate 25 weight percent zinc chloride solution. Discharge through a 10~000 ohm resistor gave a discharge voltage of 3.5 volts and a 34,228-F -17-.

- ., ,.,, ~ " i .

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3.~37 discharge current of 100 microamps, Di~charge time was 10 hoursO
Exampl~ 4 The ~ame procedure that was u~ed in Example 3 waq ~ollowed9 except that the braqs platee were sub~tituted with platinum plates~ The discharge values through a 10,000 ohm re~istor were es~entially the aame. Thu~5 there is little difference seen between the u~e o~ brass or platinum plate~0 Example 5 The 3ame procedure that was u~ed in Example 1 wa~ followed, except that a di(triethylene glycol butyl ether)terephthalate 25 weight percent calcium iodide ~olution wa~ substituted ~or both the di~triethylene glyeol butyl ether)terephthalate 25 weight percent 20 lithium iodide ~olution and the di(triethylene glycol butyl ether)terephthalate 25 weight percent zine ¢hloride ~olution. Discharge through a 10,000 ohm re~istor gave a discharge voltage o~ 3.5 volt~ and a di~charge amperage of 100 microamps. Di3charge time was 10 hours.
Example 6 The procedure of Example 5 was followed, except that aluminum plate~ were u~ed in place of the brass plates~ The di~charge values through a 10~000 ohm resistor were e~sentially identical as thoqe reported in Example 5.

34,228-F 18-.~ :
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:

1. A secondary battery which comprises:
(a) an ionically and electronically conductive first polymer film having substantially uniformly distributed therewithin a reactive electrochemical species which contributes to the ionic conductivity of said first polymer film and which is electrochemically reduced when aid battery is being discharged and electrochemically oxidized when said battery is being charged, (b) an ionically and electronically conductive second polymer film having substantially uniformly distributed therewithin a reactive electrochemical species which contributes to the ionic conductivity of said second polymer film and which is electrochemically oxidized when said battery is being discharged and electrochemically reduced when said battery is being charged, and (c) an ionically conductive third polymer film in contact with said first and second films, said third film comprising:
(i) a polymer, (ii) a plasticizer for said polymer, and (iii) an electrolyte for said battery which is disassociatingly solubilized in said plasticizers said plasticizer and the solubilized electrolyte being substantially uniformly distributed within said polymer, said third film being substantially electronically non-conductive under discharging voltages and electronically conductive under charging voltages, and (d) a first electronically conductive collector in contact with said first polymer film and a second electronically conductive collector in contact with said second polymer film.

2. The secondary battery of Claim 1, wherein said collectors are selected from graphite, plastic/graphite composites, or metal.

3. The secondary battery of Claim 2, wherein said first and second collectors are of metal selected from Al, Cn, Pt, Ag, Au, brass, or alloys thereof.

4. The secondary battery of Claim 1, wherein said first film comprises:
(i) a polymer, (ii) an agent for rendering said first film electronically conductive, (iii) a plasticizer for said polymer, and said reactive electrochemical species comprising:
a salt disassociatingly solubilized in said plasticizer, said salt having the formula MXa wherein M is an alkali metal ion, an alkaline earth metal ion, a zinc ion, a copper ion, a mercury ion, or a silver ion; X is 34,228-F -20-a halogen ion or an acetate ion; and a is the oxidation number of M, and wherein said second film comprises:
(i) a polymer, (ii) an agent for rendering said second film electronically conductive, (iii) a plasticizer for said polymer, and said reactive electrochemical species comprising:
a salt disassociatingly solubilized in said plasticizer, said salt having a constituent with an electrode potential less than M and having the formula M'Xb wherein M' is an alkali metal ion, an alkaline earth metal ion, a zinc ion, a copper ion, a mercury ion, or a silver ion; X is a halogen ion or an acetate ion; and b is the oxidation number of M'.

5. The secondary battery of Claim 4 9 wherein MXa is selected from CuCl2, CaI2, and LiI; and M'Xb is selected from ZnC12 and CaI2.

6. The secondary battery of Claim 4 or 5, wherein the salt concentration in the plasticizer is from 5 to 30 percent of total salt saturation.

7. The secondary battery of Claim 4, wherein said plasticizer in said first, second, and third polymer films is an alkyl ether ester of an acid selected from benzoic acid, terephthalic acid, phthalic acid, adipic acid, and mixtures thereof.

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8. The secondary battery of Claim 4, wherein said plasticizer in said first, second and third polymer films is an alkyl ether ester of terephthalic acid having the formula:
wherein R1 is a phenyl radical or aliphatic hydrocarbon radical of the formula CnHm wherein n is an integer of 1 through 8 inclusive and m is equal to 2n + 1; R2 is either hydrogen or a methyl radical; x is 2, 3, or 4;
and y is 2, 3, or 4.

9. The secondary battery of Claim 8, wherein said plasticizer in said first, second, and third polymer films is di(triethylene glycol butyl ether)terephthalate.

10. The secondary battery of Claim 4, wherein aid plasticizer is present in said first and second polymer films in an amount of from 5 to 50 weight percent based upon the total weight of said polymer, said plasticizer, and said salt in each of said films;
and wherein said plasticizer in said third polymer film is present in an amount within the range of from 5 to 40 weight percent based upon the total weight of said polymer, said plasticizer, and said electrolyte in said film.

11. The secondary battery of Claim 4, wherein said polymer of said first, second, and third polymer films is selected from poly(vinyl chloride), polyurethane, polystyrene, chlorinated polyethylene , 34,228-F -22-poly(vinylidene chloride), and poly(ethylene terephthalate).

12. The secondary battery of Claim 19 wherein said electrolyte is selected from alkali metal tetraphenylborates and alkali metal thiocyanates.

13. The secondary battery of Claim 12, wherein said electrolyte is sodium tetraphenylborate and is present in an amount of from 1 to 7 weight percent based upon the total weight of said polymer, said plasticizer, and said electrolyte in said film.

14. The secondary battery of Claim 4, wherein said electrically conductive agent is selected from graphite, finely divided carbon, or other electronically conductive species.

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