An improved silver-zinc battery particularly suited for use in an environment where battery operation is subjected to multiple charge/discharge cycling over extended periods is described. The battery seperator system, containing a highly absorbent material continguous with the surfaces of the plates and multiple semi-permeable membranes interposed between the plates, is also characterized

Bogner, R. S.

Farris, C. D.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE-ADMINISTRATION
WASHINGTON. D.C. 20546
(NASA-Case-flPO-11806-1) STOBAGE BAITERY
COMPRISING NEGATIVE PLATES OF A W E D G E
ATTNYOTF° GP ! SHAPED .CONFIGURATION Patent ( N A S A ) 6 p
i CSCL 10C
H7U-196935
Unclas
00/03 30286
TO:
FROM:
KSI/Scientific & Technical Information Division
Attn: Miss Winnie M. Morgan
GP/Office of Assistant General
Counsel for patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code 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.
 :
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 NO
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. Woerner
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19740011580 2020-03-17T14:47:37+00:00Z
Unitejd States Patent
Fletcher et al.
t i l ] 3,790,409
[45] Feb. 5, 1974
[54] STORAGE BATTERY COMPRISING
NEGATIVE PLATES OF A WEDGE-SHAPED
CONFIGURATION
[76] Inventors: James C. Fletcher, Administrator of
the National Aeronautics and Space
Administration with respect to an
invention of; Richard S. Bogner,
Altadena, Calif.; Charles D. Farris,
Flemingsburg, Ky.
[22] Filed: Feb. 22, 1972
[21] Appl. No.: 228,163
[52] U.S. Cl 136/20, 136/30
[51] Int. Cl ' HOlm 43/00
[58] Field of Search 136/30-31,6,65,
136/20,95, 102, 143, 146-147, 100, 111
608,216 8/1898 Ogden 136/102
1,332,483 3/1920 Bridge 136/155
2,727,083 12/1955 Hollman et al 136/30
3,216,859 11/1965 Duncan 136/6
3,450,566 6/1969 Solomon et al 136/6
3,493,434 2/1970 Goodkin 136/30
3,501,350 3/1970 Horowitz 136/20
Primary Examiner—Anthony Skapars
Attorney, Agent, or Firm—Monte F. Mott et al.
[57] ABSTRACT
[56]
1,149,665
1,149,666
916,320
References Cited
UNITED STATES PATENTS
8/1915
8/1915
3/1909
Mason 136/111
Mason 136/111
Joel 136/14
An improved silver-zinc battery particularly suited for
use in an environment wherein the battery operatively
is subjected to multiple charge/discharge cycling over
extended periods. The battery is characterized by a
plurality of positive plates of a planar configuration
having interposed therebetween a plurality of negative
plates of a wedge-shaped configuration and a separa-
tor system including a highly absorbent material con-
tiguous with the surfaces of the plates and multiple
semi-permeable membranes interposed therebetween.
5 Claims, 5 Drawing Figures
PATENTED KB 51974
3,790.409
SHEET 1 OF 2
"HO
/8
PATENTEOKB 51974 3,790,409
SHEET 8 OF 2
/VG. 5.
3,790,409
- ' 1 2
STORAGE BATTERY COMPRISING NEGATIVE oxygen recombination rate by about 35 percent on
PLATES OF A WEDGE-SHAPED CONFIGURATION open circuit and by 15 percent on overcharge.
ouiriM np iMvcMxir»w A Stora8e battery of a type similar to that hereinbe-
UKIUIIN Uf UN v UN IIUIN
 fore mentioned jg more fally described in United States
The invention described herein was made in the per- 5 Letters Patent No. 2,727,083.
formance of work under a NASA contract and is sub- Hence, it should be recognized that there currently
ject to the provisions of Section 305 of the National exists a need for a practical solution to the perplexing
Aeronautics and Space Act of 1958, Public Law problem of overcoming the effects introduced through
85-568 (72 Stat. 435; 42 U.S.C. 2457). the so-called shape-change phenomenon which in-
„ ^ --, ~ ~ ~r~ ™.^ *»,. ,,~»,^,~., 10 volves a redistribution of the active or negative compo-BACKGROUND OF THE INVENTION
 of ^  ^ e,ectrode wfth
 P
1 . Field of the Invention current density.
The invention relates generally to electric storage
batteries and more particularly to an improved silver- OBJECTS AND SUMMARY OF THE INVENTION
zinc battery particularly having an increased cycle life. 15 It is therefore an object of the instant invention to
2. Description of the Prior Art provide an improved electric storage battery which
It is, of course, well recognized by those familiar with overcomes the aforementioned disadvantages.
the design of systems employed in storing electrical en- Another object is to provide an improved electric
ergy that silver-zinc storage batteries have certain char- storage battery suitable for use in an environment
acteristics which render these batteries particularly de- wherein extensive charge/discharge recycling is re-
sirable over other storage batteries, particularly in in- quired.
stances where high energy density, high rate capability, It is another object to provide an improved negative
and low capacity loss are of a primary concern. plate for use in a rechargeable electric storage battery
It also is well recognized that in such batteries the po- of a type which employs a fluid electrolyte.
rosity of the negative plates affects cell performance. Another object is to provide a separator system for
For example, it is accepted that the relative capacity use in silver-zinc batteries.
and the average ampere-hour efficiency of batteries It is another object to provide in a storage battery an
provided with zinc plates rapidly increase as the poros- improved plate having a silver grid coated with a nega-
ity of the zinc electrode or plate is increased from 60
 30 live active composition and which overcomes the in-
percent to 80 percent. herent shape-change phenomenon involved in redistri-
In practice, zinc- plates often are fabricated by em- bution of the negative composition during cycling.
ploying, as a negative composition, zinc-oxide and a It is another object of the instant invention to provide
mechanical binder such as Teflon and polyvinyl alcohol in an electrical storage battery a negative plate of a sub-
and the like. This composition is applied to a grid, 35 stantially uniformly contoured wedge-shaped configu-
formed of such material as silver, and sintered. In form- ration, including a grid of a planar configuration em-
ing zinc plates present production methods frequently bedded in an homogeneous mass of a negative compo-
' require that a mixture of zinc-oxide, binders and addi- sition selected from a class of composition which in-
tives by dry-pressed onto a grid of silver placed in a eludes zinc.
mold conforming to desired dimensions. Where pre- 40 These and other objects and advantages are achieved
ferred, zinc can be deposited on a suitable grid, through through the use of a plurality of positive plates of a pla-
electrical deposition, with the plates thereafter being nar configuration, each including a silver grid embed-
rolled or pressed to a desired thickness. As a practical ded in an homogeneous mass of a positive composition
matter, electrical connections are made in any suitably selected from a class of composition which includes
manner, such as by welding or mechanically fastening 45 powdered silver, a plurality of negative plates alter-
a lead wire to the grid. nately interposed between the positive plates, each
One of the notorious difficulties encountered in em- being of a substantially uniformly contoured, wedge-
ploying zinc plates employing either of the aforemen- shaped configuration and includes a grid of a planar
tioned techniques is that the contour of the zinc plates configuration formed of a metallic silver embedded in
often undergoes a change caused by solution and re- 50
 an homogeneous mass of a negative composition se-
precipitation of the zinc-oxide as the cells cycle be- lected from a class of negative compositions including
tween a charged and discharged condition. Particularly zinc-oxide, and a separator system interposed between
in gravitational fields, the contour tends to thicken the positive and negative plates including an absorber
toward the lower part of the electrode as cycling occurs of a substantially inert highly absorbent material con-
causing the plate to be thickened with an attendant re- " tiguous with the positive and negative plates and a plu-
d action in total available surface area. In an attempt to rality of semi-permeable membranes interposed there-
overcome this innate tendency, various binders have between.
been suggested. However, in most instances cycle life nPSCRIPTION OF THF DRAWINGS
has not been improved and in many instances a reverse BRIEF DESCRIPTION OF THE DRAWINGS
effect .has been achieved. For example, it was found FIG. 1 is a perspective view of a secondary electric
that carboxymethylcellulose in concentration above storage battery which embodies the principles of the
0.5 percent decreased cycle life by migrating toward instant invention.
the positive electrode where it reacted with silver-oxide FIG. 2 is a perspective view of a plate-pack without
to deposit reduced silver on the separator system.
 6J a normally related separator system, employed in the
While 1.7 percent Teflon added to zinc-oxide powder battery depicted in FIG. 1, illustrating one arrangement
was found to double the cell life a distinct disadvantage for the positive and negative plates employed therein.
attends its use, since the Teflon additive reduced the
3,790,409
FIG. 3 is a perspective view of a grid employed in fab-
ricating the negative plates shown in FIG. 2.
FIG. 4 is a perspective, partially sectioned view of
one of the negative plates shown in FIG. 2.
FIG. 5 is an enlarged, fragmented, cross-sectional
view of a portion of the plate-pack depicted in FIG. 2,
illustrating a suitable separator system as operatively
employed in separating the positive and negative
plates.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
Referring now to the drawings wherein like reference
characters designate like or corresponding parts
throughout the several views, there is shown, in FIG. 1,
a silver-zinc electric storage battery 10 which embodies
the principles of the instant invention.
As shown, the battery 10 includes a battery case 12
having orthogonally related walls 14 and a top closure
member 16 arranged in substantial parallelism with a
bottom closure member, not shown. From the top clo-
sure 16 there protrudes electrodes 18 and 20 which, in
practice, extend through the top closure member 16. A
bus bar 22, FIG. 2, and electrical leads 24 serve to cou-
ple the electrode 18 with a plurality of positive plates
26. In a similar fashion, the negative electrode 20 is
coupled with a plurality of negative plates 28 through
a bus bar 30 and suitable leads 32. Foe reasons which
should readily be apparent, the particular manner in
which the plates 26 and 28, respectively, are coupled
to the electrodes 18 and 20 can be varied as desired.
For example, the leads 32 may, if desired, be welded to
both the plates and the bus bars to thus establish an in-
tegrated unit.
It is to be understood that the positive plate 26 forms
no specific part of the instant invention. Accordingly,
a detailed description of this plate is omitted in the in-
terest of brevity. However, it further is to be under-
stood that the plate 26 is fabricated in a manner consis-
tent with currently employed techniques, including
pasting silver or silver-oxide and a suitable binding ma-
terial to a silver or nickel grid. If preferred, powdered
silver or powdered silver-oxide and a binder are
molded into sheets and then pressed into the grid.
Where silver-oxide is employed, the pasted plates are
sintered so that the silver-oxide is converted by thermal
decomposition to silver and the organic additives are
burned off. Grid thickness, silver density, and plate
thickness, of course, are varied to suit intended uses.
As shown in FIG. 3, each of the negative plates 28 in-
cludes a grid 34 onto which a negative active composi-
tion 36, FIG. 4, is deposited by any suitable technique,
including dry-pressing a mixture of zinc-oxide, binder
and adhesive onto the grid placed in a mold conforming
to the shape and dimension of the negative plate 28, as
by depositing zinc onto a grid and then rolling or press-
ing the plate to the required contour.
The contour of the negative plate 28 conforms to a
uniform, wedge-shaped configuration thicker at the top
than at the bottom. Preferably, the plate 28 is twice as
thick at the top as at the bottom, however, the specific
relationship in dimensions is varied according to im-
posed parameters. Accordingly, it is to be understood
that the negative plate of the instant invention is a po-
rous negative plate of a' substantially uniformly con-
toured, wedge-shaped configuration and includes
therein a grid of a substantially planar configuration
10
15
20
25
30
35
45
50
„
embedded in an homogeneous mass of a negative com-
position, selected from a class of compositions which
includes zinc-oxides.
As best illustrated in FIG. 5, the positive plates 26
and the negative plates 28 are separated by a separa-
tory system, generally designated 40.
Broadly, there are three categories of separators,
namely cellulosics, non-cellulosic synthetic material
and inorganic separators. Separators also serve special-
ized functions as silver-migration limiters, zinc-
penetration limiters and electrolyte absorbers. As em-
ployed in the instant invention, the separator system 40
includes a negative absorber 42 wrapped about each of
the wedge-shaped negative plates 28 and a positive ab-
sorber 44 wrapped about the positive plates 26.
In practice, the negative absorber includes multiple
layers of a regenerated cellulose of a type sometimes
referred to as fibrous sausage casing. The negative ab-
sorber 42 serves to hold a quantity of electrolyte in
contact with the negative plate while inhibiting zinc-
dendrite growth by reducing zinc penetration.
The positive absorber 44 of the separator system 40
preferably is formed of an irradiated polypropylene.
Accordingly, it can be seen that the positive absorber
44 is a relatively inert material which is placed next to
the positive 'electrode to assist in inhibiting silver-
migration and to absorb electrolyte.
Between the negative and positive absorbers 42 and
44, respectively, there is interposed a plurality of semi-
permeable membranes 46 also formed of fibrous sau-
sage casing, or irradiated polyethylene grafted with
methacrylic acid. It is, of course, important to under-
stand that the membranes 46 function to separate the
absorbers 42 and 44 while accommodating a passage of
electrolyte and ions therethrough during cycling. While
various electrolytes can be employed, potassium hy-
droxide functions quite satisfactorily for this purpose.
It is to be understood that through a use of the
wedge-shaped negative plates and the separator sys-
tem, which includes both positive and negative absorb-
ers separated by multiple layers of semi-permeable
membranes there is provided an improved electric stor-
age battery which combines the characteristics of a sil-
ver electrode with those of a zinc-electrode and which
is electro-chemically reversible.
Although the invention has been herein shown and
described in what is conceived to be the most practical
and preferred embodiment, it is recognized that depar-
tures may be made therefrom within the scope of the
invention, which is not to be limited to the illustrative
details disclosed.
What is claimed is:
1. An improved rechargeable battery for storing elec-
trical energy including:
A. a plurality of positive plates of a planar configura-
tion, each comprising a silver grid embedded in an
homogeneous mass of a positive composition se-
lected from a class of compositions which includes
. powdered silver;
B. a plurality of negative plates alternately interposed
between said positive plates, each of the negative
plates being of a substantially uniformly contoured,
wedge-shaped configuration and comprising a grid
of a planar configuration formed of metallic silver
and embedded in an homogeneous mass of a nega-
3,790,409
live composition selected from a class of negative
compositions which includes zinc-oxide;
C. a separator system interposed between said posi-
tive and negative plates including an absorber of a
substantially inert, highly absorbent material con-
tiguous with the surfaces of the positive and nega-
tive plates and a semi-permeable membrane inter-
posed therebetween; and
D. a battery case including means defining a bottom
and a top closure member and opposed sides dis-
posed in normal relation to said plates.
2. The improvement of claim 1 wherein the absorber
is irradiated polypropylene.
3. The improvement of claim 1 wherein the absorber
is a highly absorbent cellulosic material.
4. The improvement of claim 1 wherein the mem-
brane is regenerated cellulose sheeting.
5. The improvement of claim 1 wherein the mem-
brane is irradiated polyethylene.
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Storage battery comprising negative plates of a wedge shaped configuration

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