A flexible separator is reported for use between the electrodes of Ni-Cd and Ni-Zn batteries using alkaline electrolytes. The separator was made by coating a porous substrate with a battery separator composition. The coating material included a rubber-based resin copolymer, a plasticizer and inorganic and organic fillers which comprised 55% by volume or less of the coating as finally dried. One or more of the filler materials, whether organic or inorganic, is preferably active with the alkaline electrolyte to produce pores in the separator coating. The plasticizer was an organic material which is hydrolyzed by the alkaline electrolyte to improve conductivity of the separator coating

Sheibley, D. W.

English

NASA Technical Reports Server

,0V.UTIO^
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
W A S H I N G T O N , D.C 2054G
UN 2 6 WQ
HCI'LY TO
ATTN OF QP
TO:
FROM:
NST-44
XK^Scientific & Technical Information
Attn: Miss Winnie M. Morgan
,GP/Office of Assistant General
Counsel for Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in
In accordance with the procedures agreed upon by Code GP and
KSI, the attached NASA-owned U.S. Patent is being forwarded for
abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No. 4,0*5,341
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent Case No.
NOTE - If this patent covers an invention made by a corporate employee
of a NASA Contractor, the following is applicable:
YES
Pursuant to Section 305(a) of the National Aeronautics and Space Act,
the name of the Administrator of NASA appears on the first page of the
patent; however, the name of the actual inventor (author) appears at
the heading of column No. 1 of the Specification, following the words
"...with respect to an invention of ..."
*'
Bonnie L. Henderson
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19780017587 2020-03-20T13:29:55+00:00Z
United States Patent
Sheibley
[ii]
[45]
4,085,241
Apr. 18, 1978
[54] INORGANIC-ORGANIC SEPARATORS FOR
ALKALINE BATTERIES
[75] Inventor: Dean W. Sheibley, Sandusky, Ohio
[73] Assignee: The United States of America as
represented by the United States
National Aeronautics and Space
Administration, Washington, D.C.
[21] Appl. No.: 720,521
[22] Filed: Sep. 7,1976
[51] Int. C1.2 H01M 3/02
[52] UJS. Q 427/385 B; 427/385 C;
429/254
[58] Field of Search 429/136, 254, 251, 246;
427/391, 385 B, 385 C; 260/42.14, 42.5, 42.32,
42.33, 875, 876 B, 876 R, 878 B
[56] References Cited
U.S. PATENT DOCUMENTS
3,239,478 3/1966 Harlan 260/876 X
3,542,596 11/1970 Arrance 429/254 X
3,625,771 12/1971 Arrance et al 429/136
3,639,508 2/1972 Kambeur 260/876
3,749,604 7/1973 Langer et al 429/136
3,861,963 1/1975
3,880,953 4/1975
3,917,607 11/1975
Arrance et al 429/136 X
Downey 260/876 B
Grassland et al 260/876 X
Primary Examiner—Michael R. Lusignan
Attorney, Agent, or Firm—N. T. Musial; J. R. Manning;
J. A. Mackin
[57] ABSTRACT
There is disclosed a flexible separator for use between
the electrodes of Ni-Cd and Ni-Zn batteries using alka-
line electrolytes. The separator is made by coating a
porous substrate such as sheets or mats of asbestos or
other materials with a battery separator composition.
The coating material includes a rubber-based resin co-
polymer, a plasticizer and inorganic and organic fillers
which comprise 55% by volume or less of the coating as
finally dried. One or more of the filler materials,
whether organic or inorganic, is preferably active with
the alkaline electrolyte to produce pores in the separa-
tor coating. The plasticizer is an organic additive such
as a material which is hydrolyzed by the alkaline elec-
trolyte to improve conductivity of the separator coat-
ing.
17 Claims, No Drawings
p&SA-Case-LIi-126l*9-1> IBOBG1BIC-OBGMIC
•SEP1BMOBS FOB-»lKllin B1TTEBIES *«£»*
(NASA) 4 p CSCI 10C
00/43
H78-25530
Onclas
22U63
4,085,241
1 2
A further object of the invention is to provide a po-
INORGANIC-ORGANIC SEPARATORS FOR rous, flexible separator which greatly extends the life of
ALKALINE BATTERIES Ni-Cd and Ni-Zn alkaline batteries.
/-MJT/- KT <-»c -rue TKn/civrT-T^vT ^n additional object of the invention is to provide aORIGIN OF THE INVENTION
 5 separator for airline batteries using nickel electrodes
This invention was made by an employee of the for one pole, which separator utilizes low cost materi-
United States Government and may be manufactured or als.
used by or for the Government of the United States It is yet another object of the invention to provide a
without the payment of any royalties thereon or there- flexible, porous, alkaline battery separator having good
for. 10 conductivity although containing an amount of poly-
meric material greater than 40% by volume of dry ma-
BACKGROUND OF THE INVENTION
 terials in ^ amount of filler material, by volume of dry
This invention relates to battery separators and is materials less than 60%.
directed more particularly to a separator for use be- DESCRIPTION OF A PREFERRED
tween the electrodes of Ni-Cd and Ni-Zn alkaline elec- " EMBODIMENT
tromotive force (EMF) cells or batteries.
In recent years there has been an upsurge of interest According to the invention, a flexible porous battery
in the electric automobile due to pollution problems separator for an alkaline cell is made by coating a flexi-
with internal, combustion engines and, also, because of ble> P°rous substrate with a slurry comprised of a co-
the energy crisis. Accordingly, there has been a parallel 20 P°lymer or rubber based resin, a plasticizer, which
increase in work on batteries or cells suitable for power- reacts with the alkaline electrolyte to produce a short
ing electric vehicles cham (two or three carb°n) alcohol or glycol, trichloro-
Lead-acid batteries have been used in the past for ethylene or chloroform an inorganic or organic filler
electric automobiles and are currently in use for dollies ^mch * mert to *f alkallnue .****«*& ™* * P^e-
and vehicles used in factories. The high-weight and " [onmng morganicfiller which ,s reactive with the alka-
expense which results from providing a sufficient num- 1"le ^ ^ ^ pref"red electrolVte ls KOH al"
ber of batteries to achieve a practical range of operation th™gh,.Na°H Can be T , ,,
 u ,
for an electric automobile is too great to make such ^ flexlble Porou,s sfubstrate 'an be asbestos ?£eets °,r
vehicles acceptable to the general public.
 m other non.woven substrates such as nylon or other pol-
„ . ... .. > , .« , j • j v .* 30 ymenc matenals known in the prior art. Because of thePnme candidates to replace the lead-acid battery are
 flexj u of ^
the Ni-Cd and Ni-Zn alkaline batteries. However it has ^
 in
 y
accordance ^ the invention, the slurry of
been found that the nickel electrodes of such batteries
 in ic ator material ^ ,ied to a Jov.
are subject to warping after relatively short usage^ This .
 web of flexib,e substrat£ matefial b automated
requires that the separators between the nickel and zinc
 35 j t. ne coati is then dried and> „ permitted
or cadmium electrodes be highly flexible so as to pre-
 by the hi h f^^ty of the coati the coated sub.
vent cracking and disintegration of the separator and
 strate is collected on a roller.
the consequent shorting of the electrodes. -j^
 because the battery separators made in accor-
Another objective which must be met with regard to
 dance with the invention may be easily processed me-
Ni-Cd and Ni-Zn alkaline battenes is the reduction of
 w chanically, production costs are kept low. The substrate
cost to an acceptable level. Because the cost of the
 material may be formed into boxes or envelopes to
separators is a significant portion of the total cost of an enclose a battery electrode as taught by the prior art.
Ni-Cd or Ni-Zn alkaline cell, a reduction in the cost of -T^JS
 may be done either befOre or after coating the
manufacturing separators is an important factor. Thus, a substrate material.
separator which utilizes low cost materials and which is
 45 According to the prior art, particularly as taught by
easy to manufacture is desirable. U.S. Pat. No. 3,861,963 to Arrance et al, the amount of
OBJECTS AND SUMMARY OF THE ceramic powder and potassium titanate fibers together
INVENTION m an alkali"6 battery separator should be at least 50%,
and preferably substantially greater than 50% of the
It is an object of the invention to provide highly
 50 mixture, and the amount of either the ceramic material
flexible separators for use between electrodes of Ni-Cd
 Or the potassium titanate can be less than or in excess of
and Ni-Zn alkaline EMF cells. 50% of the mixture. The patent further teaches that,
It is also an object of the invention to provide such ordinarily, the inorganic or ceramic material is present
separators which are, in addition to being flexible, in major proportion and the potassium titanate in minor
highly resistant to damage from alkaline electrolytes. 55 proportion. Further, the amount of polymeric material
It is another object of the invention to provide alka- can vary widely and can constitute as much as 50% or
line battery separators which may be produced very
 mOre of the mixture, but under these conditions the
inexpensively by automated machinery. result is a separator of increased internal resistance,
Another object of the invention is to provide battery although having greater flexibility,
separators which strongly inhibit zinc dendrite and 60 According to the prior art, in preferred practice the
nodule growth in Ni-Zn alkaline batteries. organic polymeric material is employed in minor pro-
Still another object of the invention is to provide a portions to obtain sufficient bonding and porosity to
flexible separator having a surface which is continuous afford substantial flexibility. The organic polymeric
and free of defects and wherein the interior structure of material preferably ranges from about 2% to about 35%
the separator coating is comprised of particles and voids 65 by weight, according to U.S. Pat. No. 3,861,963 to
which are relatively uniform in size and distribution to Arrance et al at column 8, lines 26 through 46.
achieve a uniform current density over the surfaces of Applicant prefers that the polymeric or rubber based
the electrodes. resin materials be greater than 50% by weight up to
4,085,241
80% by weight of the inorganic-organic separator coat-
ing material. This is made possible by use of plasticizer
which reacts with an alkaline electrolyte to form short
chain (2 or 3 carbon atoms) alcohol or glycol, thereby
decreasing resistivity of the separator material. By vol-
ume, Applicant's invention utilizes 10-50% filler mate-
rials in the finally dried separator coating with about
30% being preferred.
According to the prior art, the filler material used for
the mixture. The plasticizer is added after th^rubber ,
based resin or polymer is dissolved and the mixing is
continued.
The filler materials are placed in a porcelain ball mill
and the mixture from the blender is then added. Alter-
natively, the filler materials may be added to the mix-
ture in the blender and thoroughly mixed in.
This composition is then placed in the ball mill. The
ball mill is operated for sufficient time to produce a
battery separator for alkaline batteries were inert mate- 10 smooth, lump-free slurry. In general, this step takes on
rials such as potassium titanate, calcium stabilized zirco- the order of at least 20 hours.
nium oxide, magnesium silicate, zinc silicate, iron sili- The slurry is then coated onto an asbestos sheet or
cate and materials such as alumino silicates. In separa- other web-type substrates at about 10-20 mils wet thick-
tors embodying the present invention, a reactive filler ness. The coating may be applied by using a roller^ a
material selected from the group consisting of calcium 15 knife edge or by dipping the asbestos sheet in the slurry
silicate, silicon dioxide (silica) and alumina having a or by automated equipment. The coating is then dried
particle size of from 0.01 micron (0.01 X 10~6 meters) to
3 microns, when incorporated in the other unreactive or
inert filler material(s), react with the alkaline electrolyte
to form pores in the separator coating. 20
The reaction of the CaSiO3 with the alkaline electro-
lyte, for example, produces a flocculent precipitate
which, together with the inert filler material, reduces
the diameter of the pores present in the finished separa-
tor. When one of the electrodes is Zn, the small pore 25 ethylene-butylene rubber. Other types have polybutadi-
size retards movement of zincate ions through the sepa- ene midblocks or polyisoprene midblocks.
(dry thickness: 1.5 to 3.5 mils) and yields a flexible po-
rous separator suitable for use in an alkaline battery,
particularly a battery using KOH electrolyte.
The rubber based resin or polymer is a block copoly-
mer selected from the group of thermoplastic rubbers
consisting of chains of three blocks - an elastomeric
block in the center and a thermoplastic (polystyrene)
block on each end. The elastomeric midblock is an
rator to minimize the growth of zinc dendrites which
can short-circuit the electrodes, for example, between
Ni-Zn. When SiO2 is used as a pore forming filler, the
flocculent precipitate does not form.
It is believed that the calcium silicate reacting in the
alkaline-rich electrolyte forms a low molecular weight
soluble silicate and insoluble calcium hydroxide. The
calcium hydroxide may be capable of reaction with
Very good separators have been produced where the
coating includes a copolymer of styrene and ethylene-
butylene rubber. One such copolymer is Kraton G.
30 The plasticizer is preferably, but not necessarily, se-
lected from materials which react with the alkaline
electrolyte to produce a short chain (two or three car-
bon atoms) alcohol or glycol for good conductivity.
Commercially available epoxidized soyabean oil has
zincate ion, thus forming insoluble calcium zincate. The 35 been found to make a very satisfactory plasticizer. Poly-
silicon dioxide appears to react with the alkaline elec- meric polyester plasticizers of ethylene or propylene
trolyte to form soluble polymeric silicate anions.
Inert filler materials which have been found to be
satisfactory for use in alkaline battery separator coat-
ings embodying the invention include low cost materi- 40
als such as various titanates, mixed silicates, zirconates
and/or organic materials such as polyethylene spheres,
wood flour, cotton flock, lignins, or naturally occurring
fibrous materials having a fiber diameter or particle
diameter from about 0.1 micron to 20 microns. 45
TABLE I
50
INGREDIENT
Rubber based
resin
Chlorinated
hydrocarbon
solvent
Plasticizer
Calcium Silicate
Inert Fillers
Silica
alumina
No. 1
50
600
20
50
25
2
No.
50
650
20
50
'. —
2
2 No. 3
50
600
—10 to 100
—
—
No. 4
50
600
20
—25
—
— —  10-100
Separator Coating Composition, Parts by Weight
No. 5
40-60
As
required
20-50
10- 100
10- 100
2-20
10-100
Referring now to Table I above, there are shown
formulations for 5 alkaline battery separator coatings
made in accordance with the invention. The steps in
making each of the five exemplary battery separator
coatings are as follows:
The copolymer or rubber based resin powder is dis-
solved in one or more chlorinated hydrocarbon solvents
such as chloroform or other suitable solvents such as,
but not limited to, toluene or trichloroethylene by sub-
jecting the mixture to heat. Preferably, this is done by a
high speed blender which causes high shear forces in
glycol and azelaic acid as well as polymeric or polyester
plastidizers of ethylene or propylene glycol and adipic
acid have been found to be suitable in this application.
Lead titanate and calcium silicate as inert and reac-
tive fillers, respectively, when combined with the co-
polymers and plasticizers previously described as in
Example 1 of Table I and coated on a paper substrate,
for example newsprint, form a superior alkaline battery
separator.
The flexible substrate to which the separator coating
is applied may be any desired thickness. However, the
object of flexibility is very important and mandates a
relatively thin substrate. Fuel-cell grade asbestos sheets
about 10 mils thick are very satisfactory. Ordinary
newsprint (paper) when coated with the separator mate-
rial of the instant invention makes an excellent separator
for use between the electrodes of an alkaline battery.
The materials listed in Table I are intended to be
55 exemplary and not limiting. Solvents other than trichlo-
roethylene or chloroform may be used and the amount
may vary the requirement being that the rubber based
resin or polymer is seen to completely dissolve although
this may not be true in a strict chemical sense.
60 As indicated previously, the rubber based resin or
copolymer comprises between 50 and 80% by volume
of the separator coating material. The filler material,
that is a reactive filler material and an inert filler mate-
rial, comprise from less than 50% down to about 25%
65 by volume of the separator material formulation with
about 30% being preferred.
Of the filler materials used, it is preferable that the
reactive filler material be less than 50% by volume of
\4,085,241
5 6
the total filler material. The inert filler material may 5. The method of claim 1 wherein said slurry includes
include one or more inert-filler materials mixed in van- between 50-80 volume percent of said thermoplastic
. rubber,
ous proportions.
 6 -^ method of claim l wherein ^  slurry coating
It will be understood that changes and modifications
 5 is from about 10 to about 2Q mils thick,
to the abovedescribed invention may be made by those 7. The method of claim 1 wherein said slurry is corn-
skilled in the art without departing from the spirit and prised of parts by weight: 40-50 of rubber based resin;
scope of the invention as set forth in the claims ap- sufficient solvent to dissolve the resin; and 10 to 100 of
nded hereto calcium silicate.
wu * • i •' ^ • 10 8. The method of claim 7 and including by parts
wnat is claimed is: weight: 10 to 100 of at least one inert filler; 2-20 of silica
1. A method of making a flexible, porous, separator
 and 1(MOO of dumina.
for an alkaline EMF cell comprising the steps of: 9. The method of claim 8 and including by parts
dissolving in a solvent a thermoplastic rubber of the weight: 20-50 of a plasticizer selected from the group of
type made up of chains of 3-blocks wherein the 15 esters consisting of hydroxyethyl and hydroxypropyl
middle block is an elastomer and each end block is esteis of '^P10 aad azeli&c acids.
. , ... 10. The method of claim 8 and including by parts
thermoplastic;. weight: 20-50 of epoxidized soyabean oil.
mixing a first filler material inert to said alkaline elec-
 u ^ method of c]aim j wherein ^  substrate is
trolyte and a second-pore forming filler material
 2o paper.
reactive with said alkaline electrolyte; 12. The method of claim 1 wherein said solvent is a
combining the filler materials and the dissolved ther- chlorinated hydrocarbon solvent.
moplastic rubber to form a slurry; 13- The method of claim 12 wherein said solvent is
coating said slurry on a flexible non-metallic sub- ch!°ro^rm . . , . . ,
 L . ._, ,. .8
 j
 25 M The method of ciaim j wj,erem sajd flrst lnert
strate; and jyler is jead t^nsite and ^4 second pore-forming filler
drying said coating. is
 caicium silicate.
2. The method of claim 1 wherein a polyester selected is. The method of claim 14 wherein said calcium
from the group of esters consisting of hydroxyethyl and silicate is less than 50% by volume of the total filler
hydroxypropyl esters of adipic and azelaic acids is 3° material.
added to the dissolved thermoplastic rubber. 16 ™e method °f ^aim 15 wherein the total filler
„ _ t_ j » i • , \_ • - j - j material is between 25% and less than 50% by volume3. The method of claim 1 wherem epoxidized soya-
 Qf ^  s,urry exdudmg ^ ^^
bean oil is added to the dissolved thermoplastic rubber.
 17 -j^ method of claim 1 wherein said thermoplastic
4. The method of claim 1 wherein said elastomer is 35 rubber is polystyrene,
ethylene-butylene rubber. * * » * *
40
45
50
55
65


Inorganic-organic separators for alkaline batteries

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server