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Патент USA US3022377

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Feb. 20, 1962
c. HoRoWlTz ET AL
3,022,367
sEPARAToR FOR ELECTRIC BATTERIES
Filed April 23. 1958
-60
- 50 KMnO4
No
-40
- 30
-20
-lO
2O
30
8O
70
40
50
60
70
\
I
8O
90
IOO
O
20
IO
O
POLYVINYL ALCOHOL (PVA)
60
50
40'
30
METHYL CELLULOSE
INVENTORS.'
CA RL HOROW/ TZ
MEYER ME/VDELSOH/V
BY
auf@
/ AGE/vr
ice
`United lStates Patent
1
.' ’
2
3,022,367
.
, In addition, they possess the ability to adhere firmly to
" a supporting base, such as, for example, nylon fabric or
,
felt, glass-Wool mats, cellulosic sheets and fabrics, viscon
casings, and webs of rayon and other electrolyte-resistant
SEPARATOR FÜR ELECTRIC BATTERIES
Carl Horowitz, Brooklyn, and Meyer Mendelsohn, New
synthetics.
. York, N.Y., assignors, by mesne assignments, to Yard
ney International Corp., New York, N.Y., a corpora
tion ofV New York
p
3,022,367
Patented Feb. 20, 1962
The film-forming ability of the homogeneous mixture
embodying this invention may be further enhanced, if
A
Filed Apr. 23, 1958, Ser. No. 730,474
desired, by adding oxidation-resistant plasticizers such
14 Claims. (Cl. ISG-_146)
as, for example, glycerols or glycols, and/ or anti-oxidants
such »as M (p-hydroxyphenyl) morpholine marketed un
der the trademark “SoluX.”
The invention will be more fully described with refer
ence to the accompanying drawing in which:
FIG. l is a representation of abattery incorporating
separators according to this invention; and
f
The present invention relates to inter-electrode sepa
rators for electrochemical cells..
v This application is -a continuation-in-part of our ap
plication Ser. No. 469,292, filed November 16, 1954, now
abandoned,> for Separator for Electric Batteries.
Among materials heretofore proposed for inter-elec
trode separators are -polyvinyl alcohol, methyl cellulose,
wood, paper and regenerated cellulose. As lthe stand
FiG. Q. is a graphic representation of the properties of
separator films compounded in accordance with this in
ards of performance for batteries were raised, these
known separators no longer met all'requirements for
vention, plotting the electrolytic resistance and the oxida
combined resistance is the sum total of their individual
this invention.
tion resistance as a function of the separator composi
`
mechanical and electrical strength, electrical character 20 tion.
FIG. 1 is a representation of atypical liquid-electrolyte
istics and length of life. The prior art has taught that
cell embodying this invention, having a casing 11 and
separators could be constructed by placing layer upon
a cover 11a with a pair of negative electrodes 12 and
layer of the above materials to form composites, in` at
a positive electrode 13 within the casing 11. The elec
tempt to meet the more vrigorous requirements. Each
layer, however, would then maintain its individual char 25 trodes are separated from each other by layers of inter
electrode separator materials 14 and 15 according to
acteristics as against the succeeding layer so that their
resistances.
The general obiect of this invention is to provide a
new type of separator material having low electrolytic
electrode conductors 12a and 13a.
trodes. The electrodes and the separator materials are
completely permeated by the electrolyte, which may be
Another object of this invention is to provide a sepa
rator material resistant to oxidation while maintaining
V
acidic, neutral or alkaline.
The separators of this invention may also be used in
'
so-called dry cells, i.e. cells Where the major portion of
the liquid electrolyte is absorbed to form conductive
pastes. The electrolytes »in such cells may also be acidic,
>neutral or alkaline, and the choice of the particular
separator materral according to this invention is then
A further object of this invention is to provide a sepa
rator for electrochemical cells which will withstand pene- A
tration ofl active electrode materials while having the
ability to resist attack by the oxidizing agents participat
ing in the electrochemical reaction, at 4the same time ex
governed by the solubility of the film~forming composi
hibiting the low electrolytic resistance necessary of high~
rate batteries.
The casing is filled
30 with electrolyte to a level 16 above the tops of the elec
resistance.
high electrolytic conductivity.
The electrodes are connected to positive
and negative terminals (not shown) by their respective
`
tion in the particular electrolyte. Y Among the various
'
types of dry cells there should be included, by way of
example but not -for purposes of limitation, mercury cells,
Another object of this invention is to provide a re
chargeable cell .with a separator system having elec
trolytic conductivity and great oxidation resistance.
m-anganese-dioxide cells, and lead-peroxide cells.
that a separator can be prepared from homogeneous
mixtures of polyvinyl com-pounds and film-forming, _elec- l
different aforementioned polyvinyl compounds with only
FIG. 2 shows a representative curve for various pro
A more particular object of this invention is to pro 45
portions of films cast from mixtures of polyvinyl alcohol
vide a film-forming separator m-aterial with the afore
(PVA) and methyl cellulose. The polyvinyl alcohol 4is
mentioned properties and capable of forming a coating
shown as representative of the general class of polyvinyl
on an electrochemically inert support of negligible elec
compounds encompassed by this invention and is not
trolytic resistance.
.
50 meant to limit our invention to this compound. The
We have found, in accordance wi-th this invention,
general shape of the curve is the same for each of the
slight differences in the numerical values. Curve A is
a plot of the electrolytic resistance as a function of the
ethers). The mixtures when cast into films, upon either 55 methyl-cellulose
content of the film. The conductivity,
temporary or permanent supports, produce separators
of course, is a reciprocal function of the resistance.
with oxidation resistance as great vas that known to the
Curve B is a similar plot of the permanganate` number
art and with extremely ¿high electrolytic conductivity not
as a funotion'of the iilm composition. This permanpreviously associated with oxidation-resistant materials.
ganate number is a representation of the amount of
Among the vinyl Ycompounds'capable 'of forming
trolyte-swellable. cellulose ethers (including carboxy
homogeneousandruni-form mixtures with the cellulose
60
ing substances liberated by one gram of the film in a
ethers vare ` polyvinyl .-alcohol, “ polyvinyl-methyl-ether/
maleic-acid‘ _copolymer (PVM/MA), polyvinylpyrroli
done and its copolymers with suchvsubstances as vinyl
alcohol 'and vinylacetate. The mix-tures are all capable
of being cast on a glass surface or the like into self 65
supportingfilmsor membranes or into interfibrous films
upon fibrous supports.
The films
are all electrolytically
Y
conductive but electronically resistant.
,Films produced from the foregoing substances, and
embodying the present invention, a-re distinguished> -by
semi-permeability as well as structural uniformity as
evidenced by resistance to gasV diffusion‘and penetration.
potassium permanganate needed to neutralize the reduc
quantity of electrolyte in which the film has been soaked
for 48V hours. The permanganate number provides a
measure of relative oxidation resistance of the various
»materials used for separators. The lower the perman
ganate number, the greater the .resistance of the material
.f ; to oxidation. Itwill be apparent from reference to FIG.
2 that pure methyl cellulose has desirable oxidation
resis-tance characteristics but has too high an electrolytic
70 resistance for use in batteries designed to supply current
at medium and high rates.
YIt will be 4noted that the ratio of methyl cellulose, rep
3,022,367
3
4
resenting the cellulosic solids, to polyvinyl alcohol, repre
senting the vinylic solids, can safely range between 1:3
20% and 80% by weight of said film, with methyl cel
and 3:1.
lulose.
Below the above-mentioned lower limit the
electrolytic conductivity of the liilms falls rapidly and cells
manulac'tured from such materials have intolerably >high
internal resistance.
,
2. An interelectrode separator for electrochemical cells,
comprising a semi-permeable film composed of a homo
geneous mixture of a polyvinyl ìeeompound, in la propor
Similarly, above the upper limit it
has been found that the oxidation number of the sepa
tion rangingv‘bet-ween l20% yto 80% by weightfof said film,
with methyl cellulose.
rator material indicates a low order of oxidation resist
3. A-n interelectr'ode :separa-tor for lelectrocliemical cells,
ance which cannot safely be tolerated in electrochemical
comprising a >semi-permea'lile film fcomp'of'sed of ‘a homo
cells that must -be stored or stockpiled for any consider 10 geneous mixturey of polyvinyl alcohol, §i-n a `proportion
able period of time.
ranging `between 20% 4and 80% by weight of said film,
with methyl cellulose.
4. An interelectrode separator for electrochemical cells,
Example 1
A viscous liquid is prepared by mixing the following
comprising a semi-permeable íilm composed of a homo
ingredients:
15 geneous mixture of polyvinyl-methyl-etherïmalcicanhy
Y
dride, in a proportion ranging between'20'% 'and 80% 'by
Grams
Methyl cellulose, 5% vaqueous solution _________ __ 100
10% aqueous solution PVM/MA _____________ __ 100
weight of said ñ-lm, with methyl cellulose. ~ Y
PVA, 10% aqueous solution __________________ __
Die'thylene glycol ___________________________ __
40
6 20
Solux (anti-oxidant) _________________________ __
0.1
comprising a 'semi-permeable film formed of >aïhomogene
ous mixture o'f polyvinyl acetate, in a proportion ranging
between 20% 'to -80% Iby Weight of 'said 'lilmïwithzmeth’yl
cellulose.
6. An interelec‘trode ’separator Vfor electrochemical cells,
comprising a semi-permeable tilm ‘formed of 'a homogene
The mixture is stirred until it is completely homogeneous.
A thin layer is cast on glass and allowed to dry at room
temperature vfor 4 hours in a current of dry air. The lre
5.. An 'interele'c-trode separator Lfor'¿electrochei'nical cells,
sulting film is Stripped from the glass. A -cell using this 25 ous mixture of `a polyvinylpyrrol'idone copolymer, in a
proportion ranging between 20% and '80% -`-by weight of
lilm as inter-electrode separator between a Zinc negative
elect-rode and a lsilver positive electrode has substantially
greater cycle life than a control cell using an equivalent
thickness of cellophane as the separator.
said >film with methyl cellulose.
`
7. An interelectrode separator for electrochemical cells,
comprising a semi-permeable :film composed _of a >homo
30 geneous mixture -of a polyvinyl compound in a` propor
tion ranging between '20% and 80% of 'said iilm, `said
Example 2
compound being substantially insoluble injalk'a‘line solu
The mixture of >Example 1 is applied to a .permeable
tions, with methyl cellulose.
`
'
backing such as a fabric by dipping the fabric into the
8. An interelectrode separator ffoi- electrochemical cells,
solution, removing the excess by calender rolls `and then
drying the permeable support in a current of low-humid 35 comprising a semi-permeable lilm .composed of 'a homo
geueous mixture ‘of a :polyvinyl compound, in a propor
ity air. The resulting separator, when used in a silver
t-ion ranging ‘between 20% and 80% of said Íil'm, said
zinc cell, is found to reduce the zinc-penetration rate for
such cells.
compound lbeing substantially .insoluble 'in y‘acidic electro
Example 3
lytes, and methyl cellulose. l
A -rnixïture having the following îformula:
p
.
9. An electrochemical -cell `comprising ‘at least one neg
ative electrode, at least one positive electrode, an electro
lyte vand an interelectrode separator Ib'etween 'said nega
lGrams
10% methyl-'cellulose solution __________________ _ A100
A10% PVA lsolution __________________________ __ 100
Diethylene glycol __ _____ __ __________________ __
>6
‘tive and ‘positive electrodes, said ‘separator comprising
an ’electrolyte-permeable film ’composed of a homogene
ous vmixture of a polyvinyl compound, in a proportion
is applied to a polyester-fiber Vfabric (Dacron by Du Pont) 45 ranging between 20% ’and v'80% Vbyweight `of said iilrn,
by dipping. The excess is removed, after Vimpregnation
with methyl cellulose, said ‘cor'npound being 'substantially
is complete, »by means of a blade. Dry cells are pre
pared using the 'above material in place of 'the conven
insoluble insaid electrolyte.
_,
:
1-0. An 'electrochemical cell according to, lclaim 9,
tional starch-impregnated paper. Such cells ’furnish
wherein said 'separator “further -comprises la ‘permeable
higher currents -with no substantial change in polariza 50 support for ysaid iilm 'resistant `to ‘said electrolyte.
-tion time. In addition, the cell capacity is maintained
ll. An lelectrochemical vcell according ‘to Aclaim 10,
even after vprolonged storage at elevated temperature.
wherein said support comprises a porous 'polymeric :sheet
Example 4
material.V
l
`
l2.
cel-l according to fcllaim ‘10, wherein "said support
A mixture of the following formula is `applied to îDac 55 comprises a web ofsynthetic iibers.
ron fabric:
13. A cell according yto claim l2, wherein ïsaid 'fibers
Grams
consist oÍf nylon.
‘25% methyl-cellulose solution_____ ___________ __ 125
'20% jpo’lyvinylpyrrolidone Vsolution (average molec
Vulm-_weight60,000) ______ _.. _______________ __
v75
v
i
,
l `-14. An intcrelec'trode separator Jforlan ‘electrochemical
60 device comprising -a =sem`iépermeable .lilm .composed of a
The fabricl treated as above is used as an inter-electrode
homogeneous .mixture .of la. polyvinyly compound 1in a .pro
portion ranging 'between ¿0% to r80% Íby weight .of :said
í?ilm Vand methyl cellulose, said A:polyvinyl compound Ãbeing
‘selectedpffrom vthe Igroup vconsisting :of ¿polyvinyl alcohol,
polyvinyl-methyl ether/amaleic-a’cid compolymel?, ëp‘ûly
Vseparator in a ~silver-zinc alkaline battery. The -cell is
then subjected 'to a rapid charge/ discharge .regime and Ahas
a .much improved cyc-le life over that of conventional
65
separators.
vinylpyrrolidone, -fpolyvinylpyrrolidon‘ewinpyl -’alcohol .cof
-It -is understood that the above examples have been
,polymers yand l:polyvinyl alcohol-Minyl racetate'copolymens.
cited :to demonstrate general techniques and that 'they in
no way are intended to limit the linvention Ywith respect
to quantities Vor composition.
70
We claim:
1. Aninterelectrode separator for electrochemical cells,
comprising va permeable support coated with a >semi-per
meable film composed of a homogeneous mixture of Ia
polyvinyl compound, in a proportion >ranging rbetween 76
'References zCited in 'fthfe ïlìl‘e î'o'f'lthís fpatent
UNITED STATES PATENTS
2,345,629
12,5 ’34,3 3 6
3,022,367
UNITED STATES PATENTS
2,549,101
2,558,662
2,591,755
2,635,127
Koch _____________ __'.-.... Apr. 17, 1951
Norris _______________ _.. I une 26, 1951
Wilson et a1. __________ _.. Apr. 8, 1952
Yardney et a1 __________ __ Apr. 14, 1953 5
6
2,729,694
Ellis _________________ _- Ian. 3, 1956
2,747,009
Kirkwood et a1 ________ _.. May 22, 1956
2,795,009
2,854,338
Gosnell et al. ________ __ June 11, 1957
Herrick et a1. ________ __ Sept. 30, 1958
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