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LEAD STORAGE BATTERY WITH EXPANDER SUPPLY

Abrégé anglais

LEAD STORAGE BATTERY WITH EXPANDER SUPPLY
ABSTRACT OF THE DISCLOSURE
The electrodes are supplied with expander material
by providing a storage container with corrodible walls
located in the acid electrolyte, which liberates its contents
only after the original expander content of the negative
active mass has already been significantly depleted. The
wall material is either a plastic having limited acid resistance,
or one of the metals Pb, Sb, Sn, or an alloy thereof. When
using Sb, there exists a combined supply of expander and
antimony. The latter counteracts the tendency toward crumbling
of the positive mass which exists in Sb-free plates.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A lead storage battery having a supply of expander material for
location within electrolyte of the battery, from which supply the expander
material is suppliable to the electrolyte at least during a portion of the
life of the storage battery, the supply of expander material being at least
initially separable from the electrolyte by a barrier material which is slow-
ly dissolvable in the electrolyte to thereby liberate the expander after a
predetermined time.
2. The lead storage battery of claim 1 wherein the barrier material
is a synthetic plastic.
3. The lead storage battery of claim 1 wherein the barrier
material is a metal.
4. The lead storage battery of claim 3 wherein the metal is lead,
antimony, tin, or an alloy of at least two of these metals.

Description

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SY~ [F':[CArr`ION
The inventiorl relates to a lead storage batLery hav:irlg
a sllpply o:f expander material located wi.thill the electrolyte,
:Erom ~h:ich the expander is resuppli.ed durillg at le~ast a portion
oE the :I-i.Ee o:E the storage battery.
Fxpallder add:itives to the negat:ive acti.ve mass are
:i.nt:ende(l to counteract the formation oE compact lead crysta:Ls
by inLerferillg wi.th :lead sepa:rat-ion during charg:ing, and
thereby to mainta:in the highly porous s-tructure o:E the elec~trode
p].ate~s. Suita~le expander materials are ba:riurll sulphate,
high molec.ular organic substances, particu:larly l:i.gnin
derivatives, or coloring materials such alizarirl .red :Erom
the ser-.ies of hydroxyanthraquinolles.
~ ccclLIse the expander materials have si.gni.ficant solubili~y
:Ln su~l.phur:ic acicl, there takes place a progressive leaching
out of thc negative e].ectrodes, with the expander also reaching
the positive e:Lectrodes in the course oI cyclical operation,
where it is destroyed through oxldation. The consequellce
o~ this loss of expander is a decrease in capacity andl :Eor
starter batter:i.es, particularly a reduction in their performance
in cv:Ld starts. The use of h:i.g}ler initia:L expandeI quantit:i.es
in the rllass c:ompos; tions has been of on].y lim:itetl remedia:L
e~:fect for this short:com:ing because -this increased in:itial
concentration was accompanied by a spreading ef:Lect in the
ear:Ly stages of the storage battery liEe which substantiaLly
exceeded the degree necessary in order to ach:ieve a predetermined
currerlt: de'Live:ry capability.
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In accordance w:itll German Patent :l~uh:L:i.cclt:ion ~O.E~enle--
gllrlgssc~lrift) ~,~55,3:1.3 it. Ilas there:Eore a1.rea(ly heen propose(l
io store expander rnater:ial in 1 vessel. whic}l is in commuTl:icatio
w:i.th the aci d electrolyte through a small Opell:ing, SO that
thcre ta~es place delivery o:E expander contirluousl.y, as a
furlctiorl of the cross-section of the opening, the satl1ration
concerl~-ratio!l, and the difEusi.on coef:Eic-ients, over an exterl(led
period o:E time. 'l'he drawback o.E this ar:rangmenl: is that the
delivery o:[ spreader mater:i.al from the storage starts as soon
as the cel.:L is .E:illed.with the acid. Due to this unrestricted
start of the addition of stored material to th~ normal delivery
of expander :Erom the negative p].ates theIe a:rises~;n over-
supp:ly, -in a manner sirnilar to that previous~l.y desc:ri.bed above.
'l'he reasorl i.s that, in a new storage battery ce:L:I.,
the quant:ity of spreader materlal in the negative mass is
:ini.tia:l:ly made su:Eficient for several. hundred cyc:Les.
~ ccordi.ngly, it is an object of the p:resent inventi.on
to provi de a storage arrangement for the ex~parlder m.ltcri.al
:in such a manner that .i.ts.consumption is llrevented at least
i.n the early stage of the storage battery l.:i.fe, and that it
is suppl:ied only Lrom a subsequent point in t:i.me, progressively,
an(l in accordance w:i.th the true need.
Th-i.s and other objects lhich wil]. ap~pecll^ are achieved
in ac(:ordance with thc! invention by separat.i.ng tlle expander
supply l.rom the elect3-olyte by a barr:ier materiLI~l., which disso:lves
s-Lowly in the electrolyte and li.berates the expander af-ter
a predc~l:ermi.nlbll~ ti.lile period~

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llpon the start o cycl:ical operation9 the barrier materiaL
:is perlllallently sllbjected to a corrosi.ve alternating attack
:in Lhe surrourlcl:ing, su.lphuric ac:id contain~ g n~edium. Th:is
mecl:i.um ~:irsL causes an oxidative decompos:itiorl of the barrier
nlater:ial, wh:ich initially p:~ovides an inperrneab:Le wal.l between
the spreader and the electro~yte. However, :i.t :is only aEter
a preclete:rminecl time that the inEluence o:E thc decompos:ing
:for.e- ,o welkens the barrier parti-ti.on that ;.t ruptures i.n
places, and the expander material which is there no ].onger
protectecl :is taicen up by -the su:Lphuric acid, oxid:izes, and
begins to dissol.ve. The conti.nuing destruction oE the wal:l
causes the resupply of expander material to both electrode
polar:it:i.es to continu~ steadily, so that good current loaù
capacity an(l mass uti.liYation are assured at least :Eor an
aclclitio~ l po:rtion of the storage battery l:i:Ee.
A suitab].e wall material for the expander supply embodying
the :invent:ion is Syntlletic pl.astic. Included7 fo:r this purpose,
are all synthetic resin products whicll have lim-ited resistance
to a sul.phuric acid medium, both pure po.Lymers~ as well as
co- or homo-polymers. These products may exh:ibit the most
varied degrees of corrosion resist:lnce, not only because of
the:ir chemical structure, but also because oE aclcl:it:i.ves o:E
softeners and stabiliY.ers, so that a user has a wide choice
with respect to a suitable wall materia:l..
As the principal parameter influencillg the corrosi.on
speed o:E a synthetic p].astic, there may be cons-iclered its
degree Or polymeri7ation. Tllils, a low po].ymcr:ic syTIthctic
.resin product clecomposes more~ rapidly than a high polymeric

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pro(lucL wiLh corresl)c)l-ldirlgly higll molecu:Lar we:ight. Unclc!r
the preva:i~ing circumstances, t}le decomyosit:i.on duration o.f
a p:Lastic, l~h:i.Ch o:E course also clepends uporl wall. thicl<ness,
CaTI vary from a few months to many years. ~xarnp:l.es of plast:ics
which are suital)le :For the invent:ion are: polyv:inylchloride,
polys~ Eonates, epoxy resins, po:l.yethyleneterephtllalate,
polybut~l.enetereplltllalate, polyethy]elle, polypropylelle, poly-
i.et::r~LIuoret}ly:l.erle, polytrifluo;-ochl.oroeL}Iy]er~e. Howevc~r,
th:is lisl::ing is not to be considered as e~clusi.ve.
Anotller sui.table wall material for the expander supply
embodying the invention may be a metal, beca~se its at-tack
hy corrosi.on proceeds relatively uniform:Ly and in a speci:Eic
manller. However, there are preferably selected such metals
as do not detrimenta:Lly influence the electrochemiccll per:Eormance
o:E -thè ceJ.l, e:ither at all, or to a neg:l.ig;b:Le extent. Particularly
des:irable :E:rom th:is standpoint within a lead storage battery
are lecLd, antimony, or tin, including b;.nary and ternary alloys
o:f these metals. An antimony membrane would hclve the add;tiollal
aclvantage that -l:he expander snpply secondari:l.y Eunctions as
an antimr-ny supply, sincr-~ the progressive dissolut;.on of tl-le
barrier wall causes antimony in the form of ant-imony conta:i.nillg
3-- and 5- valenced ani.ons (SbOSO~, [H5n 5Sbll5nl ) migrates
to the electrodes and advantageous]y inf]uences at least
the behav.ior o:E the posit:ive electrode. Th:is i.s because,
.i.f the electrode grids are of an antimony-f.ree al.loy, e.g.
lead ca].cillm, which is desi:rable because of high hydrogen
overpotelltia], t~lell exper~ience hcls sho~n that tllese positive
e:l.ecLrocles have a tendency toward increased cr~lrnb:l..ing, a

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d:isadv.l[~iag~ whic.h grid plates ~ith anti.rnc)ny---cc,nla-;rlirlg al].oy
gri c7~s clo not exh:i.b-it clue to suf'c'iciellt antimorly presellce in
the active positive mass.
Because, on the other hand, a posit:ive elect:rode
grid of a lead antimony alloy corrodes mLIch mor~ qlliclcly than
an arltirllony--free grid, positive e:lectrocles ~;th allt~ lony-Eree
gr i dC; Call be L~sed with unrestricted advantage, when the pos;tive
active mass :i~s supp:liead with antimony for prevent:ioll of
crurnb].illg not from the grid itself, but from the corroding
snp~ly barrier wall. This arrangement embodying t.he invetltion
is particularly desirable Lor storage batteries wh:ich are
s~lbjected to a strong cyclical Load, with occas:ional deep
cliscllarge, and which contain antirnony-free grid p~Lates.