CA1304123C - Recombinant battery and plate separator therefor - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A fibrous sheet useful as a battery plate separator is disclosed. The sheet, in a specific embodiment, is made from a mixture of Grade 210 glass fibers, Grade 206 glass fibers, Grade A-20 chopped glass strand, and Grade A-121 polyethylene fibers. The fine glass fibers impart a high absorbency to the sheet; the coarse glass fibers impart a lower absorbency; and the polyethylene fibers, which are hydrophobic, are essentially non-absorbent. The different fibers are used in such proportion that the sheet has the absorbency, usually from 75 to 95 percent, required for use in a recombinant battery, even in the presence of free electrolyte.
A recombinant battery in which fibrous sheets as described above serve as plate separators is also disclosed, as a method for producing a recombinant battery which includes the steps of assembling a plurality of electrodes with such sheet separators in a case, flooding the electrodes in the case with an electrolyte, removing electrolyte that is not absorbed by the sheet separators from the case, and closing the case.
Finally, a recombinant battery in a case which has an opening is also disclosed; the opening is closed by a thin film of polyethylene or the like through which hydrogen can escape at a faster rate than oxygen.

Description

~3~ '3 Tltle: R~COM~INP,NT ;BATT~3RY AND PkATE SE;PARATOR T~EREFO~
Back~round o~ the Invention ~ield of the InventiQn This invention i5 a recombinant batter~ whereln oxyg~n ~ormed elactrolyt~cally a~ the positive pl~te~ in~ida th~
battery is able to m~grate to the ne~ative plate~ for electrolytic recombinAtion, ~ pl~ts ~ep~r~tor or ~uch battery, and a method for producin~ ~uch ~ battery. ~riefly, ths plat~ ~ep~rator i~ m~de from fibers havin~ di~ferent capabilitie~ for holdin~ electxolyte; the ~i~er~ are u~ed in such proportion~ thAt the separ~tor, even ~n the pre~ence of exc~ el~ctrolyte, is capable of holdin~ only the amount of electrolyte de~ired in the bsttery. The fiber~ having dif~rent capabilities ~or hold~n~ electrolyte c~n be, for ex~mple, coa~e ~ s fiber~ ~nd ~ine ~la~ fiber~ or mixture of ~la~ fibers ~nd polypropylene fiber~.
Def initlon~
Su~aaquantly herein, the term "percant v/v" mean~ percent by vo~ume; the term "percent ~Jw" mean~ p~rcent by wei~ht, all ~mperatur~3 ~re in C.: a~d the followin~ abbrevi~tion6 h~ve the meanin~ lndicsted: ~m me~n~ microm~ter or micrometer~ (numeric~ e~ual to mi~ron or micron~);
m51-mi~ ram or milli5~ramg; ~ r~m or ç~rRm~; kg~3cilo~r~m or kilo~rams; l-liter or liters; ml-mllliliter ~r mlllilitera;
~5 and cm=centimeter or centimete~.
~he Prio~ Art Rsaombinant bAt~ri~ h~v~ b~on known ~or a numb~r of years, beln~ dlsclo~ed, for example, in U.S. patent No.
3,36~,861, ~cClell~nd ~t al. Thi~ p~tent ~l~o disclos~ such 30 batte~ies havins~ v~nt valves th~ous;~h which S7ase~ which f orm in ~ervice can e~cape ~o preYent the build-u~ o~ an BXCe~iv~ intern~l pre~u~e. ~.S. P~tent Nv. 3,159,50~, Chreitzber5~, diE~c~o~;e~ a b~tter~ inclu~ n~ a c~ntAiner desi~ned to pr~v~nt an u~due buil~-up of hydro~en pres~ure.
Accordin~ to ~he pa~ent, the cont~iner i~ made ~vm a ma~erial ~hich exhi~ s ~ubst~ntially in~raa~ed p~xme~bility to hyd~o~en without a correspondin~ increa~e in p~meAbill~y ~o ox~en.

., 1~ i9--l 19'~ ` l L ~ 0~1~`1 Pl IF~IIJE I~ 1'3~ J~ p, ~.-J !
~1.3~4~Z3 R~om~inant b~ttery plate sep~r~tvr~ m~de from ~7la~
fiber~ of A pluralit~r of diameter~ an~ made from mixtures o;E
s~la~ fiber~ and pol~propylene fibers ~re also known. For exam~le, U. S . patent No. ~, 465, 7~8, Harr~ s, diF~lo~e~ ~las~
5 fiber ~heet material for use a~ a Rep~rator i~ an . electrochemi~l cell, e.ç~., in su~h a batter~, ~nd made from 5 to 35 percerlt by tYeight of ~la3~ ~ib~r~ le~ than 1 ,um in diameter; t~e patent also d~lo~es a 571a~ ~iber 3heet for such use wherein there ar~ f lbers o~ a continuouS r~n~e of 10 fiber diameter~ ~nd len~th3, an~ most o~ the fibers are not over 5 mm in l~n~th . U. S . pAtent ~o. 4, 216, 230, Kono e~
81., disclo~e3 gla~ fib~r ~heet materi~l for u~e a~ a pla~e ~eparator in ~;uch A bAttery, and made ~rom 5(~ to ~5 Percent by wei~ht of gla~ fiber~ les~ th~n 1 l~m in diRmeter aI2d ~0 15 to 5 per~ant by wei~ht of co~r3~r ~la99 ~ibere. ~he ~oar~er gla3~ fibers, the re~e~ence saSr~ have ~ ~iber cli~meter la~ger than 5 ,um, prefer~bly l~rç~er than 10 IJm, and it i~
adv~ntas~eou~ ~or some of th~ ~oar~er fiber!3 'tG have diAmeters of 10 ,um ta 30 ~m. U. S . patent ~Jo. ~, 373, 015, 20 P~ter~ et al ., disclo3~ eet material f or u~ 8 ~.
~3epar~tor in f~u:h n battexy, and "çompri~ing or~Anic polymeric fiber~", b~th of the exalnple3 o the r~erence describe the ~hcet materi~l a~ "5hort ~taple ~i~er polye~ter mAttin~ ~b~ut 0.3 mm ~hick", and indicate th~t the polye~tor 25 fl~r~ rano~ ~rom abou~ 1 ~m to ~out 6 ~m in diamet~r, Finally, ~heet 3eparators ~or use in conv~nti4n~1 (non-re~ombinan'c) bA~t~rieo ~nd comprlsirlsr both ~la~ ~iber~
and oraAnic f i~er~ are di~closed in a~l o~ the ~ollowin~
U. S . p~ents: No. 4, 5~9, 677, ~odendor~, No . 4, 363, 8~6, 30 Waterhou3e; ar~d No. 4, 359, 511, ~tr~empko. U. S . pa~ent No .
4, 367, ~71, Ha e~a~a, di~clo~es 9'COX`RI~! b~ttery ~epar~tor3 com~os~d o~ acryli~ ~ibril~ in an ~mount o~ up to about 10 per~er~t by weis~ht, balance srlas~ er~. J~pane~e paten~
document 55~146, 872 di~clo~e~ ~ ~e~ar~tor material 35 COlnpri~in~ ibor~ ~50-~5 ~rcent ~y wei~ht) And or~n~lc ~iber~ (50-15 perc~nt l:y weislht) . U. S. patent No.
4, 245, 0~3, Clegg et al ., ~i~close~ a ~p~r~or mAd~ b~
overlayin~ ~ ~ir~ 3heet of ~ibrou~ mat~rial in~l~din~

3 ~3~33 2~15-37 polyethylene fibers wlth a second sheet of fibrous material including polyethylene and having a synthetic pulp content higher than the first sheet. So Ear as is known, there has not heretofore been a suggestion of a plate separato-r which, when saturated with electrolyte, leaves a residuum of unfilled voids through which a gas can transfer from one plate to another because the separator is not capable of holding an amount of electrolyte which is sufficient to fill all the voids.
Summary of the Inven-tion Briefly, the instant invention is a Eibrous sheet useful as a battery plate separator. The sheet consists essentially of irst and second fibers, both of which are inert to a particular aqueous electrolyte The first fibers impart to the sheet a given absorbency greater than 90 percent relative -to the particular electrolyte, when surfactant-free, while the second Eibers which are inert to the electrolyte impart to the sheet a diEEerent absorbency less than ~0 percent relative to the electrolyte, when surfactant-free. The first and second fibers are present in the sheet in such proportions that the sheet has an absorbency with respect to that electrolyte, when surfactant-free, of from 75 -to 95 percent. Preferably, the first fibers are glass fibers, most desirably glass fibers having an average diameter less than 5 ~m.
In one preferred embodiment the second fibers are organic fibers that are hydrophobic relative to the electrolyte, when surfactant-free, most desirably polyethylene or polypropylene fibers. In another preferred embodiment the second fibers are coarse glass fibers, for example, having a diameter from lO ~m to 20 ~m~ In a third preferred embodiment there are both organic fibers that are .

~3~ 3 3a 26815-37 hydrophobic relative to the electrolyte, when sur.Eactant-free, and large diameter glass Eibers, in addition to glass fibers having an average diameter less than 5 ~m.
The invention is also a recombinant storage battery comprising a plurali.ty of electrodes in a closed case, a fibrous sheet separator as described in the preceding 11 '~1'3 I ~ JHII L-~IJF~ IE 4i'3 ~2 ~,~'60 p~r~raph betwe~n adjacent one~, of the electrode~, and body of an elec~rolyte to which the 3heet ~ep~rhtors are inert i8 ~bqorbed by esch of the ~epar~tor~ an~ maintain~d in contact with the ~dj~c~nt on~J3 o~ the electrode~3.
The inventio~ i~ al90 ~ method ~or producin~ ~
recom~in~nt stor~ge batter~. T!le method ~ompri~e~ the gtep,3 of a~oemblin~ ~ plurality of electrode~ with a ~he~t ~ep~rAtor a.~ de~cribed above between ad~acent one~ o~ the elect~ode~ ln ~ ca~e havin~ arl openin~ in at le~3t one w~11, introducin~ A ~uantltY 0~ an el~ctrolyte ~ufficle~t to cover the alectrodel3 lnto tha ~ace, removing electrolyte that is not ~h~orbed by the sheet ~ep~rator~, the plateF" and other int~rnQ~ Bur~aces that are wetted by the electrol~te, and clo3iny the ca~. If de3ire~, the c~8e can be evacuAted partlally be~o~e the el~ctrolyte i~ i~troduc~d; in f~c~, thi~ is u~ua~ly de~irable ~o increa~e the r~te at which the cell~ Are filled. In a preferred embodiment o~ the method, thQ battery i~ formed while the electrolyte cov~r the electrode~. In another preferred embodiment A portion of the ,~0 ele~troiyte that i~ ~o~ retained by the sapara$o.~, the pl~e~ an~ the internal ~urface~ that are wetted i~ lef~ ~n the c~0~, or ~11 the 01~ctrolyte that ia not ret~ine~ is removed, and ~ desired ~mount o~ electrolyte i~ introd~ced ~efor~ the ca3e i~ clo~ed 80 ~hAt, ln either ca~e, the batter~ cont~in~ ab~orbed electrolyte and a ~ump of electrolyt~ that i~ no~ ab.~r~ed. ~he ~ctroly~e ~ump can b~ rel~tlvely ~mall or relatively lar~e, which ~ pre~erred d~pendin~ upon the ~ervice f or whiah the battery i~
intende~
Fin~lly, the invention i~ Rl~o a re~om~inan~ b~ttery h~vin~ a~ openi~ th~t i~ clo~ed by a comp~ra~ivel~ thin ~lm o~ ~olyethylen~, p~l~pro~ylene, or oth~r material that mor~ pervious ~o hydro~en than to ox~en. It ~a~ been found that the ~A~ which nece~it~ted the ventg di~clo~ed ~y McClalland et ~1. wa~ mainl y hydro~en and ox~aen p~oduced by ale~t~oly~is o~ water. It ha6 al~o b~a~ ~ound ~hat the ~y~o~en i~ u~ually pr~e~t in ~ub~tan~iallY ~eat~r t~an the stoichiometric propo~on as a c~n~equen~e o~ r~a~tio~

~3~ 23 oE oxygen at the negative electrode, and that excess hydrogen can be vented through a thin Eil~ of polyethylene, polypropylene, or the like, in effect, removing water from the elec-trolyte until the recombination capability increases to such an e~tent that the excessive release oE hydrogen ceases, and recombination prevents excessive pressure build-up. It has also been found that recombinant batteries having plate separators according to the invention are much less subject to hydrogen accumulation in service, even in the presence oE free, unabsorbed electrolyte, than were previously known recombinant batteries, and that recombination occurs at an adequate rate in batteries with the instant separators from -the very beginning of service, without any need for drying to increase oxygen recombination capability.

Brief Description of -the Drawinas Fig. 1 is a perspective view, par-tially broken away, of a battery including separator material according to the invention.
Fig. 2 is an enlarged schematic representation of a portion of the separator material in the battery illustrated in Fig. l.

With reference to Fig. 1, a single cell battery with a total of seven plates is indicated generally a-t 10. The battery 10 comprises three positive plates 12 which are electrically connected to a positive terminal 14 and four negative plates 16 ~3~Z3 5a 26815-37 electrically connected to a negative terminal 18. The plates 12 and 16 are housed within a battery case 20 which i5 covered by a top 22. An opening is deEined in the top 22 by a boss 2~.
Separators 26 are posltioned between each positive plate 12 and each negative plate 16. The separators 26 comprise sheets of separator material that are wrapped around the bottom oE each positive plate 12 and cover both faces of each positlve plate 12.
Referring now to Fig. 2, the constituents of separator 26 are schematically represented. The separator material comprises first fibers 28 whlch have an absorbency (as defined hereinbelow) for electrolyte which is high, i.e., greater than 90 percent, and further comprises second fibers 30 which have an absorbency for electrolyte which ls low, i.e., less than 80 percent. The first and second fibers are combined in proportions which give the separator 26, when surfactan-t free, an absorbency with respect to an electrolyte of from 75 percent to 95 percent.
Third fibers 32 (shown in phan~om lines) comprising relatively large diameter glass fibers may be incorporated in the separator 26 to increase the resiliency thereof. Additional fibers 34 (shown in phantom lines) can be incorporated in the separa-tor so long as the absorbency of the separator 26, when surfactant free~
relative to an electrolyte is from 75 percent to 95 percent.
A method according to the present invention for producing a recombinant battery comprises the steps of filling the battery case 20 containing the plates 12 and 16 and the separators 26 with a quantity of electrolyte sufficient to immerse the plates 12 and 16 and the separators 26, forming the battery 10 by charging, dumping excess electrolyte and sealing the battery case ~3~ 3 5b 26815-37 20 by inserting a cap ~not shown) into the opening deflning by the boss 24 to close the bat~ery 10. As demonstrated ln the examples which follow, the invention is readily applied to multiple cell batteries.
The inventlon will be more fully understood from the following examples, which are presented solely for the purpose of illustrating and disclosing, and are not to be construed as limiting.

Example 1 A fibrous sheet plate separator material was produced from 5 parts Grade 210 glass fibers, 2 parts Grade 206 glass fibers, 1 par-t Grade A-20BC chopped glass strand, 0.7 part Grade A-121 polyethylene fibers and approximately 0.06 part sulfuric acid, specific gravity 1.835, to lower the pH of a slurry that is produced to about 3. The glass fibers used are all commercially available from Manville; the grade 206 and the grade 210 fibers are marketed under the trade designation TEMPSTRAN for use in producing battery separators. They are made from an acid resistant borosilicate glass. The grade 206 fibers have a surEace area of 1.80 m per g, a fiber diameter of 0.85 ~m. The grade 210 fibers have a surface area of 0.47 m2 per g, a Eiber diameter of 3.25 ~m. The polyethylene fibers used are commercially available from Hercules under the trade designation PULPE~ A-121. They have an average length from *Trade-mark 13~3~1~3~7 11: 9, J~H~I F~l ;PL~UE ~ J1~ .g~ ~Z~ P. ~8 O . 6 to 1. 2 mm, maxirnum 2 . O, and an aVQra~e di~meter f'rom 10 to 20,um.
The ~la~ ~nd polyethylene ~i~er~, the 3ul~uric aaid and about 250 p~rts water were charged to a pap~r-~aking pulper, and the ch~r~e wa~ beat ~or about r minute~ IO di3per~e the fiber~ w~thout causin~ breakage. rrhe re~,ultin~ pe~si~n w~ dilut~d with about 250 pa~t~ wat~r, and th~ diluted di~persion wa~ then pllmped to ~ che~t at the head of a Fourdrinier paper making machine and flowed onto the ~creen of the m~chine to produce ~ separator material having a ba~is W~i~h~ o~ ~00 ~ per m~.
A G~QUP 26 battery was built with 13 plates pe~ cell consi~tin~ o~ 7 ne~ative plate~ and 6 ~>o~itiv0 pla~e~ havin~
~ast ~rid~ ~ontainin~ approximA~ely 0.4 percent tin And O . 07 15 percent c~lcium, balance le~d. ~ach pl~te wa~ 5.625 inche~
wide and 4.75 inches tall. The po~ltive plate~ were 0.057 inch thic~, while the ne~tive plates were 0.051 ~nch thick.
Sheots o~ separator materiAl produc~d ~ de~cribed above, 10.5 inches loh~ and 6.22 inches wide, were foldcd Around the po~ltive piate~ so that the ~old wa~ at the bottom o~
the pl~e, leavin~ separator material exten~in~ about ~ inch a~ove the po~itive pl~tes an~ about 0,3 inch beyond each aide of the positiVe plat~s. Each 6tac~ o~ 13 plate~ with the ~epa~a~r materi~l between adja~en~ plRt~ ~a~ erted into a c~ll h~vin~ A rib-to-ri~ dimen~ion o~ 4 in~he~, ~o that e~ch layer of ~eparator materi~l w~s compre~sed to O . 0~0 inch be~w~en ~lAte~ . The ~embly wa~ comple~ed by making th~ in~ercell conne~tion~ And s~aling a aOVRr on the bRttery co~ainer. The cell~ ~ere fille~ ~ikh a ~ul~uri~
a~id electroly~e to a level about one inch ~bo~e ~he tops of the platee . The electrol~te w~ made by addin~ 15 ~fl ~odium sulfat~ ~co s~lfuri~ acid which h~d ~ ~pe~i~ic ~ravity of 1.235~ ~he ba~t~ry wa~ then ~ormed; exces~ electr~lyte w~
dum~d; D,nd the batterY wa~ s~led.
~5 ~a~
A battery wa~ produced by the procedure o~ ~xample 1, except th~t the char~ to th~ pulper was 5.5 p~rt~ G~e 210 ~la~ ~iher~, ~.5 p~rt~ Grad~ ~06 gl~8 f ibe~ , ~ part 3 1 I~J~7 11 .~ JI~HI I P~JF r!L~ 3 ~ a~ 32~~0 P ~

A-20~C chepped s71a~s strand, O . 06 part ~ull~uric acid ar~d 250 ~?art3 water.
~xam~le 3 A batter~ wa~ produced by the procedure o~ Example 2, 5 except th~t negative plates havinr~ exp~nded metal ~3rid~ wer~
u~ ed .
For purpo~a~ of compari~on, k)ut not accordinu to the in~tant inven~ion, a control bat texy wa3 produced by the procedur~ of Example 1, except th~t the ~har~Je to the pulper 10 WA~ 5 pa~t~ ~rRde 210 gla~s fiber~, 2.5 p~rtB Gr~de ~06 ~la~ fiber~, O. OG pArt ~ul~uric a~id and Z50 par~ water.
Avera$~e v~lues were determined i~or batteries produced by th4~ fore~oin~ procedu~ o~ drg b~ttery wei~ht in ~, drained b~tter~ wei~ht in 5~, acid rete,ined in ~, acid absorb~d by 15 plate~ in g , acid retained by ~eparator~3 in ml, total ~eparator volume in ml ( cal~ulAted ~rom the known dinlen~ion~ p~rator void volume in ml (c~lculated from the tot~l ~eparator volume and ~he calculated volumes o~ tl~e fiber~ in the se~rAtO~ m~tari~1) and ~ercent v/v unfilled 20 voids in the ~eparator. The~e avexage ~ralue~ are ~et ~ rth in tho 0110wing table.
~xam~le Wu~nber 2 3 Control Dry B~tt0~ ht 11, 71611, 71~10, 95711, 736 Dr~ined El~'ctery weight14,414 14,335 13,977 15,.107 ~id ~e~ained 2, 7942, 618 3, 020 3, 371 30 A~i~ Ab~o~ hy Plste~ 1,141 1,143 1, 243 1, 232 P.cid retair~ed by Separatoxs1, 2721, 1651, 377 1, 600 Total Se~arator volume 1, 64$ 1, 6661, 6521~ 678 ~5 ~epQrQtor ~c~id volume 1, $23 1, 533 1, 527 1, 540 P0r~n~ Y/v unfilled void~ ~6.5 2~0 10,5 0.O

1CI~'19,3'' 1l: :S Jr~ F'UP~UE ~ aæ~ .3Z~l P.1~1 :~1.3~ 23 Referrint~ to the fore~oin~ t~ble, the term "ab~o~bency", A8 use~ herein and in the ~ppended claim~, i.s expres~ed in perc~nt, i~ determined by the ~rocedure described above, ~nd 5 i~ 100 minu~ e percent v/v unfilled void3.
~ atterie~ produced ~ de~cribed ~n ~xam~le 1 have been field te~ted in au~omotive servi~e. Thes~ perform 3ati~f actorily without exce~siv~ venting of ~a~, and without eXCesRive pre~sure build up, indica'cinçl th~t oxYslen f ormed 10 at the po~itive plate~ is ~ble ~o mlgrAte throu0h the sep~rator~ to the negAtive pl~te~ ~or electrolytic recombin~tion. BAt~erie~ produced by the control method, however, h~ve been found ~o ~e un~ati~factory. There is an cxae~sive pre~ure build-up, requi~int~ that gas be vented and indicat~n~ th~t o~y~en i~ not able to mi~rAte throu~h the ~epa~ator~ to the ne~ativ~ plates. ~ctual te~t data from f ield te~tint~ o~ batteries prcduced as describ~d .in ~xample 1 ~ndicate that ~hey can be u~ed wi~h computer controlle~
Alternator~ which, in normal o~eration, u~ect the ~atte~y to hi~h current charging durin~ br~kin~; althou~h the~e may be ~on~e ~ build-up ~ a con~equ~nG~ uch ch~rt~int,~, ~ exce~ive pre~sure~ should not fl~velop, and recombinatio~
~hould occur quickly once ~he hi~h curr~rlt ch~r~in~ ~e~
~atterle~ ~ccordlng to the inventi~n c~ ba 4p~a~ed in any po~iti4n ~nd c~n be ~uilt in m~ny ~hape~ thA~ wer~ not ~ea~lble wlth conventional batterie~. There i~ ~ignificantly le~ explo~ion hazArd with batt~rie~ ~ccordin~ to the invent.io~ than w~th conventi~n~l batterie~ that a~e not recombinant.
~tt~rie~ produ~ed a~ desc~ibed i~ ~xample~ nd 3 ~nd ~ontrol batte~ie~ have b~en te6te~ to co~p~re the rate6 ~t whlch ox~en ~a~ ~elea~ed at ths po~itive pl~te~ wa~
recom~n~d ~t th~ negative pl~te~. The tq3~ involved cha~in~ electroly~e-flooded, Rix-cell batt~rie~ ~o~ 16 35 houro ~ a conat~nt volt~ge of 13 . 8 vol~ . Durin~ ch~r~in~, a wat~r b~th wa~ u~d to mAint~in th~ b~tter~ t~mperatllr~
at 11. The ch~r~7ing curreDt w~, m~a~ur~ at 'ch~ ~nd of the 16 hour chAr~ period. The m~joritY ~f 'che ~r~
~ , 11'~'-3 ~ ,37 1L:-,5 JI.lH~`I PIJPDI.JE 'liq ~ 2F,13 P,lL
1 3~

electrolyte in ~he batterle~ wa~ then dralned quickly, leavin~ onl~ the small amvunt of unab~orbed electrolyte that W~3 trapped within cavities in the cover and wetting the sur~ace~ of the internal ~ell part3. The drained batteri~
5 were then ~eale~:l, fitted with pre~ure relie~ valve~ ~nd a~ain charged for 1~ hour~ ~t 13 8 volt~ ~nd 11. The ch~rgin~ curr~nt was al~o determinea Rt the end of the s~cond 16 hour~ o~ charg~n~. The ter~ "~ecombin~tion Current" ls ~ub~equentlY u~ed h~rein to ~ean the ~hAr~in~
current At ~he end of the second 16 hour~ o~ chargin~ minus that ~t the end of the ~ir~t 16 hours of ch~r~in~. The RQcombination CurrQnt is rela~ed to the ~um of th~ rate at whi~h oxygen ga~ i~ bein~ rel~a~d at th~ ~o~it.ive plates ~nd the rate at whlch oxygen ~s i~ bein~ recombined at the negative plates. Avera~e value~ o~ Recomhin~tion 5urrent ~re given in the followin~ t~ble ~or b~tterie~ ~roduced a~
de~cr~bed in ~x~mples 1-3 and for contro~ batterie~.
Recombinatio~ Curr~nt, milliampere~
Example 1 87 ~x~ple ~ 99 Example 3 ~
Control 7 The te~ d~cribed ~bove ~o~ de~Rrminin~ RecQ~bi~a~ion Current flnd the d~ta in the fore~oin~ t~bl~ ~ive a qu~lit~tive indication that batterie~ produced in accordance with th~ in~tant inv~ntion exhihit ~ar better recombination ~er~orm~nce t~lan the Control b~ttery. Howe~er, that te~
~0 d~ ot take into account the ef~ect of the p~rtial pre~ure of ox~en on recomhination. ~ccor~in~ly, ~n additional tast w~ performed on the batterie~ produced ln accordanc~ ~ith ~he ~orR~oin~ exsmples to provide a m~re ne~rl~ quantitati~e mea~ure o~ th~ pex~orm~nce of th~
batt~r~e~ in term~ o~ recombination. It hA6 be~n ob3erved th~t ~he rate o~ recombinati~n o~ oxygen in a battery is ~
dire~t Punc~ n of oxy~en partiQl pr~ure in ~he ~A~tery ca~e.

ll/~lg/1~3~7 L!:41~1 JOH~`I PUR~IJE 'ti~ '. 3~1~0 P.lZ
4~L23 In accordance ~ith the te~t, a chargin~ volta~e is appli~d to a full~ char~ed battery while a ~tre~m of nitro~en i~ cau~ed to ~low therethrou~h in cont~ct with the plates, ~pflrator an~ e~ectrolyte. The current dr~wn by the b~tery i~ me~ure~. ~he ~tream ~f ni-t~o~en virtuall~
preclude~ recombination ~ecAu~ oxy~en ~u~t be available in order for r~combination to occur. When t,he parti~l pres~ure of oxygen in a b~ttery cas~ droPs to zero, so doe~
the r~te of recom~ination.
A~ter the current dr~wn by the battery under the flow of nitro~en i8 mea~ured, the nltro~en ~tre~m i replac~d with air ~nd the char~in~ voltage i~ a~ain ~pplied to the bAttery, ~nd the current drawn by ~he ~ttery i5 me~sured again. The dlfference bet~een the two meA5urements i~
r~fRrr~d to here~t~r a~ the "~ecombinin~ Current", A
2ecombinin~ Current of zero occ~rs whe~ oxy~en is not bein~
recomblned. Five batterie~ produced i~ accordAn~e with the procedure of Example 2 were ~ound to h~e an Avera~e R~combinin~ Cu~rent of 138 millia~pere~.
xemple~ ~a and 4 Batteries were produ~ed by the pro~edure of Exam~
except ~hat the ch~r~e to the pulper w~s 386 k~ of a mixtur~
compri~in~ 64 percent Grade 210 ~la~ flbers, ~6 percent Gr~de ~06 ~ flber~, 5 p~rce~t ~-20~C c~hopped ~las~
25 ~tran~ ~nd 5 p~rc~nt A-121 polyprop~lene ~ibers, ~,609 k~
of w~ter, and ~ul~uric acid in an am~unt ~ufficie~t to lower the pN of the ch~r~e to approximately 2.6. ~n the ca~e o~
~xample 4a, the ha~5 we~ht of the ~epar~to~ materi~l w~
220 ~ per m~ an~ in the case o~ Exampl~ 4b, the basi6 wei~ht o~ th~ separ~tor m~teriAl WA~ 2~0 ~ per m~.
Values wera determined for t~o ~att~rie~ prod~ced by the procedur~ of ~x~m~le 4 o~ dry b~ttery w~i~ht in ~, drained buttery wei~ht in ~, a~id ret~in~d in q, acid absorbed hy pl~te~ in g, a~id xe~alned b~ ~e~arAtors i~ ml, tot~l ~e~rator ~olu~e in ml tcalcul~t~ fro~ the known dimen~ion~, sep~rator voi~ volume in ml ~calcul~ted ~rom the total ~epA~Ator volume and t~e ~alcul~t~d volumQ~ o th~
~ibe~s i~ th~ ~ep~r~tor mater~al) and pereent v/v unfilled (.') ? 1'3'~ ' 11 ' ll JI~IHI`I ~lJ~ uE 4i'~ ~82 3~,0 P. i3 ~.3~123 void~ in the ~epa~tor. Thesa value~ are ~et forth in the following t~ble.
ExQmple Number ~ 4 ~ry H~tt~r~ ~ight 11,757 1~,74 ~rained Ba~tery wei~ht ~4,617 14,5~4 Acid ~t~ined 2,86G 2,~3 ~0 Aci~ Ab~or~e~ by Plate~ 1,061 1,062 Acid retnined by S~parators1,~10 1,380 Total Separator volume ~,680 1,674 Separator void volume 1,532 1,540 Percent v~v un~ d voids ~,0 10.4 The Xecomb~ning Current wa~ determin~d f~r batterie~
produced a~ de~ri~ed in ExAmples 4A ~nd ~ At 6everAl di~ferent elec~olyte volume~. ~u~t before the~e determina~ion~ were m~de, the ~att~rie~ were refilled with 2S electrolyte ~o that the plate~ in ea~h cell were ~ubme~d, the ex~e~ electroly~e W~3 then du~Ped~ a~d a fir~t determin~tion of t~G R~c~mbinin~ C~rrent wa~ mad~. ~ext, ~everal ad~ition~ of elec~rolyte were made to ea~h ~attery, and Becond ~nd sub~e~uent determinations o~ Recombining 30 Cuxrent ~re m~de, one after ~a~h ~d~itien. ~t will ba appreci~ted ~h~t t~ fir~t dete~mi~ti0ns of ~ombinin~
Current ~ere made w~en the plste~ and th~ ~p~rator materia~ wer~ ~atur~ted with electrol~te And th~t ~-he ~acond ~nd ~ub~equent de~rminAtiQns w~re made when there wa~ ~x~e~s el~c~r~lyte beyond that r~quired tv ~atu~at~ the ~l~t~ and the ~epa~ator materl~l~. Th~ ge~omb~nin~ Current ~or ~ach o~ thsse te~t~ i set ~o~th in the ~v~lo~iAg table, 11'0g/'1'3~7 11:41 Jl-IH~I PlJprlLlE ~.3~ I.Z3 41~ ~f:~ 3~F,0 P.i4 to~ether with the ~mount ~i~ any) o~ electrolyte added ~ter the exce~3 wa~ f irBt dumPed:

R~COMBININ~ CURR~NT
S(milliAmPbres) Electrolyte addad toB~t~ery o~ Bett~ry of Each Cell ~ml) Example 4a Example 4b ~ 549 q98 2Q 12q 6~ -B -3* 11 75 _ - -7*
*Sinae th~ te~t i ~ccurate to only ~bout * 4 milliampere3, the e value~ ~rob~bly ~hould be con~idered to be ~ero.
The bntterie~ of Ex~m~le~ 4a and 4b exhibited recombinin~
current~ of 549 and ~9~ milliampere~, re~ectively, ~tsr the~ ~ere ~ille~ wlth electrol~te ~o th~'c the ~l~te~ were ~ubmer~ed and the exces~ el~ctrolyt~ wa~ dumpe~. They con~inued to exhibi~ su~ant~al recombinin~ current~ even ~ ter the el~atrol~te lev~1 w~s incr~sed be~nd the amotlnt th~ the pl~te~ ~nd the ~epsr&tor3 coul~ hold.
For purpo~e~ o ~omparison, but not in ACCO~ance wi~h the ln~t~n~ inven~ion, Recombinin~ Current WAO m~ured on ~everal batter~es, ~o~e m~de from ~e~ArAtor m~teri~l which is ~ur~ntly in commer~ial u~e, and ~ome ~h~ aro commorci~lly ~v~ le recombinant b~t~erie~. ~he pu~o~e o~
the te~t w~ to ~v~luate the n~ce3~ for u~n~ what McClell~nd ~t al. ~alls ~ "~tarved am~unt" o~ electrol~t~ i~
re~om~i~ant b~teri~ cont ining conventio~al ~eparator material. In ~ome c~ the ba~teri.e~ te~e~ ~ont~ d ~cpRrator materi~l ~o~po~d ~f 55 p~c~n~ o~ ~r~d~ 210 ~i~er~ ~d 35 perc~n~ r~de ~06 fiber~; ln othe~ ca~e~
~he b~tt~r~e~ w~re ~commercially avail~ble. m~d~ w~h ~e~arator m~terial which i~ b~lie~e~ t~ h~ve b~n compoged o~ 60 to ~5 percent ~ Gr~de 210 ~ib~r~ a~d 35 to 40 perc~

l/GI3 1~l:37 11:~12 :~O~I~I PU~UE ~ 3 41~3 aa~ 3~f,~ P.15 of Grade 206 ~ih~. All o~ the batterie~ test~d contain~d con~entional sulfuric acid ~lectrol~te containiny ~bout 1 per~ent of ~odium 3ul~te. ~he ~mo~nt o~ electrolyte i~ th~
batterie~ varied ~rom ~7.9 t~ 100 percent o~ the amount S requ~red ~o fill th~ void~ in the plate3 and the 8~par~or~, T~e amount of elec~roly~e required to fill the void~ waR
calculated f~om avAilable dat~ about the ~b~orptivene~s of the ~eparAtor ~at~riAl and the pl~t~. In other word~, At 100 ~r~ent, the sep~rator materiAl and the plate~ ~re ~Aturated but th~e wa~ no excess ~lectrol~te in the cell3 oP ~he battery. The dat~ concernln~ ele~trolyte l~vel~ and recombinin~ current~ is ~et forth below:
~L~CTROLY~ LEVELR~COMBINING CURR~NT
pe~cent v/v of pl~te and separator milliampere~3 s~turation 10~ o 9~ 4 88 ~7.2 ~2g ~4 9 760 9~.6 7 gO.2 1078 87.9 15gl The d~ta in the tAble above ~emonstr~te~ th~ tha q~antity o~ ele~trolyte in eae~l cell o~ ~ re~ombinant batter~ ~ith conve~tional ~eparator m~teriAl i~ critical wlth reapect to th~ rAte of r~co~b~n~tion. ~dead, ~8 the 3D qu~ntity o~ electrolyt~ in ~ach cell of ~uch ~ batt~ry approache~ l~0 percent of the amount whi~h would ~turat~
th~ ~ep~r~tor mat~ri~l And the plate~, the rate Q~
reco~bination ~ppro~ch~ o. In contra~t ~ a~ ~how~ by t~e d~ta 8e~ ~orth l~ re~pe~ o~ th~ b~tt~rie~ ~roduced in 3~ a~cordance with ~he pro~edure o~ Ex~mpIe 4, re~ombination o~cur~ a~ a ~elAti~el~ ~a~id r~te e~en when the electrolyte lavel in ~ach ~ell e~ce~d~ th~ amount ~orr*~pondin~ ~ith lO0 per~ent ~aturatlo~ o~ th~ plate~ ~nd th~ ~epar~tor material.

~3 ll/(~J~/'lq,37 11~ J~IHl`l Pl_IRrlIJE dl9 ~2 3~ J P.ll;
~.3Q~23 1~
The ~xce~sive pr~s~ure build- up o~ control b~t~erle~ cRn be relieva~ hy vent~ o~ the kind di~clo~ed l:~y kicClell~nd et al. or, accordin~ to another ~pect of the in~tAnt invention, by a~emblin~ the battery so thA~ a comp~ra~ively 5 thln f ilm o~ pol~ethylene, polypropyl~ne, or the like is the only clo~ur~ ~or ~n opening throu~h the ca~e. gu~h a ~ilm, bec~use polyethylene and polypro~ylene ar~ 1; erviou~ to hydro~en to a mu~h çlreat~r ~xtent t~n the~ are perviou~ to oxygen, enAblefi the preferenti~l relea~e of hydro~en fxom 10 'che interior of the b~ttery, di~ch~r~in~ ~:h~ b~ery. Thi~
pre~erential r~l~Ase o~ hydros7en continue~ until an electroch~ml~al balance i~ re~ch~d, ~t~r whiçh time t~e ~x~es~ive ~elfla~e o~ hydro~en, oxyç~en or both ~top~. It has been found th~t a vent openins;~ haVins7 an area of 65 cm2 15 clo~ed by A polyethylene film 0~ 025 mm thich: i~ cflp~ble o~
prefer~ntiAl velltin~ o~ h~ ogen aR required from ~ 40 amper~ hour control battery in ordinary ~utomo~ive ~erviae.
It t4ill be appreciAted that variouB chAnue~ and modific~tion~ ~n l~e made from the det~ile~ descri~tion 20 herein wi~hout dep~rtin~ from t2-e ~pirit And ~cope o~ the invan~ion ~ de~ined in the followin~ cl~im~.

Claims (15)

1. As a battery plate separator, a fibrous sheet consisting essentially of first fibers which are inert to a particular aqueous electrolyte and which impart to the sheet a given absorbency greater than 90 percent relative to that electrolyte when surfactant-free and second fibers which are inert to that electrolyte and which impart to the sheet a different absorbency less than 80 percent relative to that electrolyte when surfactant-free, the first and second fibers being present in such proportions that the sheet has an absorbency with respect to that electrolyte, when surfactant-free, of from 75 to 95 percent.

2. As a battery plate separator, a fibrous sheet as claimed in claim 1 in which the first fibers are glass fibers and the second fibers are fibers of a polymeric material which is hydrophobic relative to the electrolyte, when surfactant-free.

3. As a battery plate separator, a fibrous sheet as claimed in claim 2 in which the second fibers are polypropylene fibers, and which additionally includes such a proportion of glass fibers of so large a diameter that they increase the resiliency of the sheet after it has been compressed.

4. A recombinant storage battery comprising a plurality of electrodes in a closed case, a fibrous sheet plate separator between adjacent ones of said electrodes, and a body of an electrolyte to which said sheet separators are inert absorbed by each of said separators and maintained in contact with each of the adjacent ones of said electrodes, each of said separator sheets comprising first fibers which impart to the sheet a given absorbency greater than 90 percent relative to said electrolyte and second fibers which impart to the sheet a different absorbency less than 80 percent relative to said electrolyte, the first and second fibers being present in such proportions that each of said sheet separators has an absorbency with respect to said electrolyte of from 75 to 95 percent.

5. A recombinant storage battery as claimed in claim 4 wherein the first fibers in each of said sheet separators are glass fibers and the second fibers are fibers of a polymeric material which is hydrophobic relative to said electrolyte.

6. A recombinant storage battery as claimed in claim 5 wherein the second fibers in each of said sheet separators are polyolefin fibers, and wherein each of said sheet separators additionally includes such a proportion of glass fibers of so large a diameter that they increase the resiliency of said separator sheets after they have been compressed.

7. A method for producing a recombinant storage battery, said method comprising the steps of assembling a plurality of electrodes with a fibrous sheet separator between adjacent ones of the electrodes in a case having an opening in at least one wall, introducing into the case a quantity of an electrolyte sufficient to cover the electrodes, removing electrolyte that is not absorbed by the sheet separators from the case, and closing the case, the sheet separators being inert to the electrolyte and comprising first fibers which impart to the sheet a given absorbency greater than 90 percent relative to the electrolyte and second fibers which impart a different absorbency less than 80 percent relative to the electrolyte, the first and second fibers being present in such proportions that the separator sheets have an absorbency with respect to the electrolyte of from 75 to 95 percent.

8. A method as claimed in claim 7 for producing a recombinant storage battery wherein only a portion of the electrolyte that is not absorbed by the separator sheets is removed by the step of removing electrolyte from the case, and the case is closed containing electrolyte that is absorbed by the separator sheets and a sump of electrolyte that is not absorbed.

9. A method as claimed in claim 7 for producing a recombinant storage battery wherein all of the electrolyte that is not absorbed by the separator sheets is removed by the step of removing electrolyte from the case, thereafter a small quantity of the electrolyte is introduced into the case, and the case is closed containing electrolyte that is absorbed by the separator sheets and a sump of electrolyte that is not absorbed.

10. A method as claimed in claim 7 which additionally includes the step of partially evacuating the case before the electrolyte is introduced thereinto.

11. A method as claimed in claim 8 which additionally includes the step of partially evacuating the case before the electrolyte is introduced thereinto.

12. A method as claimed in claim 9 which additionally includes the step of partially evacuating the case before the electrolyte is introduced thereinto.

13. A method as claimed in claim 7 which additionally includes the step of forming the battery after the electrolyte is introduced into the case to cover the electrodes and before the electrolyte that is not absorbed by the sheet separators is removed from the case.

14. A method as claimed in claim 8 which additionally includes the step of forming the battery after the electrolyte is introduced into the case to cover the electrodes and before the electrolyte that is not absorbed by the sheet separators is removed from the case.

15. A method as claimed in claim 9 which additionally includes the step of forming the battery after the electrolyte is introduced into the case to cover the electrodes and before the electrolyte that is not absorbed by the sheet separators is removed from the case.