Silver-zinc cells having a separator system of cross-linked high-density polyethylene with a methacrylic acid graft withstand corrosion when subjected to thermal sterilization treatments

Bogner, R. S.

Uchiyama, A. A.

English

NASA Technical Reports Server

NASA TECH BRIEF 
July 1970
	
Brief 70-10214 
NASA Tech Briefs announce new technology derived from the U .S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Shelf and Cycle Life Evaluation of Silver-Zinc Cells 
Failure of silver-zinc battery cells is often caused 
by corrosion of the casing and electrode-separator 
materials. A study of the shelf life and recharge capa-
bilities of silver-zinc cells subjected to thermal sterili- 
zation treatments has revealed one type of separator 
material which, although not perfect, is superior to 
other materials currently used in its ability to with-
stand corrosion. 
Sterilized and control silver-zinc cells with 5 dif-
ferent separator systems were given extended shelf 
and cycle life tests. Only 6 of the 23 cells remained on 
the divalent silver-zinc upper-voltage plateau of 1.84- 
1.85 V for 12-20 months at room temperature. Upon 
discharge following the storage period, only unster-
ilized control cells with a separator system of cross-
linked high-density polyethylene with a methacrylic 
acid graft delivered capacities comparable to their 
initial capacities. 
F he cells were given several 100% depth-of-discharge 
cycles and placed back in storage for 4.5 months. Then 
these cells were cycled daily (discharged to 1.00 V 
at 9.0 amp and charged to 2.10 V at 2.0 amp) for 80 
cycles without shorting. 
The data showed that the open-circuit voltage can-
not be used to predict the capacity of a silver-zinc
cell; however, if the open-circuit voltage of a cell 
drops below 1.58 V. the cell is shorted and cannot 
he rejuvenated. 
Notes: 
Additional information on silver-zinc cells may 
be found in "Batteries for Space Power Systems", 
by Paul Bauer, NASA SP-132, 1968, for sale by 
the U.S. Government Printing Office, Washington, 
D.C. 20402; price $1.50. 
Requests for further documentation may be di-
rected to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP70-10214 
Patent status: 
Inquiries about rights for the commercial use of 
this invention may be made to NASA, Code GP, 
Washington, D.C. 20546. 
Source: R. S. Bogner and A. A. Uchiyama of

Caltech/JPL
under contract to

NASA Pasadena Office
(N PO- l 1258) 
Category 01 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
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Shelf and cycle life evaluation of silver-zinc cells

Shelf and cycle life tests on sterilized and unsterilized silver-zinc control cell

yd7& /937 
-M9 '133 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
Technical Memorandum 83-418 
S/ic/f and Cycle Life Evaluation of Silver—Zinc Cells 
R. S. Bogner 
A. A. Uch,yama 
JET PROPULSION LABORATORY 
CALIFORNIA INSTITUTE OF TECHNOLOGY

PASADENA, CALIFORNIA 
July 1, 1969 
/	 Sz -(itSj
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
Technical Memorandum 33-418 
She/f and Cycle Life Evaluation of Silver—Zinc Cells 
R. S. Bogner
A. A. Uchiyama 
JET PROPULSION LABORATORY 
CALIFORNIA INSTITUTE OF TECHNOLOGY
P ASA D E NA, CALIF OR N I A 
July 1, 1969
Preface 
The work described in this report was performed by the Guidance and Control 
Division of the Jet Propulsion Laboratory. 
JPL TECHNICAL MEMORANDUM 33-418 	 iii
Page intentionally left blank 
Page intentionally left blank
Contents 
I. Introduction	 1 
II. Background	 1 
	
Ill. Experiment	 .................2 
IV. Results and	 Discussion	 .............3 
V. Conclusions	 ................
	 4 
References ..................9 
Table 
1. Cell construction and sterilization data .........2 
Figures 
1. Cell voltage vs storage time, cell series Cl -AA, C2-AA, C3-AA, 
C1-MAA, C2-MAA, and C3-MAA
	 ..........3 
2. Cell voltage vs storage time, cell series NSNV, FSC-PF1, 
1% AA, and 2%AA
	 ..............4 
3. Cell voltage vs storage time, cell series 13Y-1C, 13Y-2C, 
13Y-3S, 13Y-4S, 9Y-1C, 9Y-2C, 9Y-3S, and 9Y-4S
	 ...... 5 
4. Cell voltage vs storage time, cell series 9PF-1, 9PF-2, 9PF-3, 
HMW-2PF, HMW-4, and HMW-5	 ...........6 
5. Capacity as a function of storage time and cycle, cell series 
C1-MAA, C2-MAA, and C3-MAA	 ..........	 6 
6. Capacity as a function of storage time and cycle, cell series 
9Y-1C, 9Y-2C, 9Y-3S, and 9Y-4S	 ...........7 
7. Capacity as a function of storage time and cycle, cell series 
13Y-1C, 13Y-2C, 13Y-3S, and 13Y-4S	 .........8 
8. Capacity as a function of storage time and cycle, cell series 
HMW-2PF, HMW-4, and HMW-5	 ..........9
JPL TECHNICAL MEMORANDUM 33-418 	 V 
Abstract 
Sterilized and control silver—zinc cells with various separator systems were 
given extended shelf and cycle life tests at the Naval Ammunition Depot 
quality evaluation facility at Crane, Ind. Six of the twenty-three cells remained 
on the divalent silver—zinc voltage plateau for 12-20 mo at room ambient tem-
perature. Only cells with a separator system of methacrylic acid graft on cross-
linked polyethylene, that were not sterilized, delivered capacities comparable to 
their initial capacities. The cells were given several 100% depth-of-discharge 
cycles, and placed back in storage for 4.5 mo. After the second storage period, the 
cells were cycled on a daily basis (discharged to 1.00 V at 9.0 A and charged 
to 2.10 V at 2.0 A). The cells delivered 80 cycles without shorting. The data 
showed that the open-circuit voltage cannot be used to predict the capacity of a 
silver—zinc cell, but if the open-circuit voltage of a cell drops below 1.58 V, the 
cell is shorted and cannot be rejuvenated. 
Vi	 JPL TECHNICAL MEMORANDUM 33-418
Shelf and Cycle Life Evaluation of Silver—Zinc Cells 
I. Introduction 
Under Contract 950364 with the Jet Propulsion Lab-
oratory (JPL), Delco—Remy (D—R) Division of General 
Motors Corp. conducted an investigation on heat sterili-
zation of sealed, secondary silver—zinc cells (Ref. 1). 
During the investigation, D—R constructed several cells 
to evaluate the effects of heat sterilization on cell com-
ponents and cell construction variations. Initial plans 
were to evaluate the effects of heat sterilization by cycling 
cells to failure; however, near the end of the contract, 
JPL decided that open-circuit shelf life would provide 
more applicable and useful data. 
This report presents the results of the extended shelf 
life tests on sterilized and unsterilized control cells. These 
tests were not completed when the final report* on the 
contract was issued by D—R. 
Those cells that had not failed before completion of 
the contract were transferred from D—R to the quality 
evaluation facility of the Naval Ammunition Depot 
(NAD) at Crane, Ind., for completion of life tests. 
'The final report is available from NASA: Accession No. N65-27367 
(15218). 
JPL TECHNICAL MEMORANDUM 33-418
Only data on cells that had not failed before the final 
report are presented herein. These data are being pre-
sented because of the exceptionally good shelf and 
cycle life attained by some of the cells, and because 
further development of some of these separator materials 
is necessary to extend the life of silver—zinc batteries. 
II. Background 
Previous work (Ref. 2) had shown that sealed silver-  
zinc cells with fibrous sausage-casing (FSC) separators 
would survive sterilization at 125°C for 36 h; however, 
when the temperature was raised to 145°C, cell capacity 
was reduced approximately 50%. Separator and/or case 
material degradation products were the prime suspects 
for the cause of loss in cell capacity. Under JPL Con-
tract 950364, D—R initiated a program to evaluate the 
effects of heat sterilization on cell components to deter-
mine what components were producing the loss in cell 
efficiency. Because separator materials were the prime 
suspect and were severely degraded in the hot electrolyte, 
D—R subcontracted a separator development program 
to Radiation Applications Inc. (RAI) to produce five 
different separator samples. Two of the separator samples 
survived sterilization; however, when sterilized in situ,
degradation products apparently effected a 30-40% loss 
in cell capacity. Auxiliary electrode measurements indi-
cated that degradation products attacked the positive 
plates, preventing the plates from accepting a complete 
formation change. 
At the conclusion of. the contract, the case material 
and separator material requirements had not been met. 
Development of a separator material to meet the ster-
ilization requirement appeared the more difficult of the 
remaining problems. A new thermoplastic polyphenylene 
oxide (PPO) that appeared to be capable of surviving 
sterilization as a case material was coming on the market. 
Work on heat-sterilizable batteries is being conducted 
by the Electric Storage Battery Co. under JPL Contract 
951296. Heat-sterilizable separator development has been 
funded under JPL Contract 951718, Southwest Research 
Institute; 951525, Westinghouse; 951524 and 951966, 
Monsanto Research Corp.; and 951091, Marmco Division, 
Whittaker Corp. 
III. Experiment 
Twenty-three cells above 1.50 V were transferred to 
the quality evaluation facility of NAD, Crane, in January 
1965. The principal variation in the design of the 23 cells 
discussed in this report concerned the separator material.
There was variation in the active material ratios and the 
number of plates per cell. These variations would have 
some effect on cycle life, but should not affect shelf life. 
The electrolyte concentration, however, might have 
some effect on shelf life. 
Design variations of the cells are listed in Table 1; the 
separator type designations are as follows: 
(1) XLHDP-AA: crosslinked high-density polyethylene 
with an acrylic acid graft produced by RAI. 
(2) XLHDP-MAA: crosslinked high-density poly-
ethylene with a methacrylic acid graft produced by 
RAI. 
(3) HMW-FSC: a special FSC material made from 
a high molecular weight cellulose fraction by 
Visking Food Products Division of Union Carbide 
under contract to D—R. 
(4) FSC: standard FSC separator material produced 
by Visking Food Products. 
(5) C19300: a treated cellophane separator produced 
by the Yardney Electric Co. 
Except for the few hours during the transfer from 
D—R to NAD, Crane, the cells were continuously at room 
ambient temperature. 
Table 1. Cell construction and sterilization data 
Material ratiob Separator Sterilization 
Cell designation Number of  Electrolyte, % of KOH 
Neg Pas Type Layers Temperature, O C Time, h plates additive 
Cl-, 2-, 3-AA 2 1 13 XLHDP-AA 4 40 Not sterilized - 
Cl-, 2-, 3 .MAA 2 1 13 XLHDP-MAA 4 40 Not sterilized - 
1 % AA 2 1 13 FSC 3 45' Not sterilized - 
2% AA 2 1 13 FSC 3 45' Not sterilized - 
9PP-1, -2,-3 1 1 9	 . FSC 3 45 145 36 
HMW-2PF 1 1 13 HMW-FSC 3 45 145 36 
HMW-4, -5 1 1 13 HMW-FSC 3 45 145 36 
NSNV 2 1 13 AA, MAA 2, 2 50 145 36 
F$C-PFI 1 1 13 FSC 3 45 145 44 
13Y-1C, -2C 1 1 13 C19-300 7 45 Not sterilized - 
13Y-3S, -4$ 1 1 13 C19-300 7 45 145 36 
9Y-IC,-2C 1 1 9 C19-300 7 45 Not sterilized - 
9Y-3S, 4$	 . 1 1 9 C19-300 7 45 145 36 
Cells containing the notation PP were preformed (charged and discharged before sterilization).
	 'Contained 1% acrylic acid. 
5AIl cells contained 2% HgO by weight in the negative plate.
	
dcontoined 2% acrylic acid.
JPL TECHNICAL MEMORANDUM 33-418 
DISCHARGED 
3.4 A-h DISCHARGED 
0 A 
C3-AA
FAILED
FAILED
2.0 
i.e 
1.6 
>
1.4 
2.0 
0
For the charge and discharge cycles, the cells were 
charged to 2.10 V at 2.0 A and discharged to 1.0 V at 
9.0 A. In storage, a cell was arbitrarily considered shorted 
when its open-circuit voltage dropped below 1.50 V. 
IV. Results and Discussion 
Figures 1-4 summarize the open-circuit voltage of the 
individual cells as a function of storage time, and provide 
some indication of the occurrence of a cell short. Figures 
5-8 show the cell capacity as a function of storage time 
and cycles. 
Figures 1-4 show that the voltage of only 6 of the 23 
cells remained at the upper-voltage plateau of 1.84-1.85 V 
(cells Cl, C2, C3-MAA; 13Y-3S, 13Y-4S, and 9Y-1C). 
Significantly, upon discharge following the storage period, 
only the MAA cells delivered capacities (20-23 A-h) com-
parable to the capacity before the storage period. 
A search of applicable literature disclosed that the 
Electric Storage Battery Co. presented some shelf life 
data over a temperature range of 90-160°F (Ref. 3).
Maximum storage time of the cells was 1 yr at 90°F, 
after which the cells showed a capacity loss of 11%. No 
other data are known that show zero capacity loss after 
20 mo of storage at room temperature. The other cells 
that survived the storage delivered only 50% or less of 
their capacity after storage of 19.5 mo. In Fig. 1, it is 
shown that all control cells with the acrylic acid-grafted 
separators had dropped to the lower-voltage plateau at 
the end of 11 mo and failed in 16-18 mo. 
Although the MAA separators were approximately 
equal to the AA separators after sterilization, the un-
sterilizable MAA separator was far superior. Because this 
work was directed toward producing a sterilizable bat-
tery, the performances of the unsterilized control cells 
were apparently overlooked as data applicable to a 
requirement for unsterilized batteries. The results ob-
tained from the three control MAA cells indicate that 
the reproduction or development of this material would 
be beneficial. 
The complete history of the control cells with the MAA 
separator is given in Fig. 5, which shows that the cells 
1.8
C3-MAA 
DISCHARGED 
21.3 A-h 
RECHARGED AND 
1.6
	 PUT IN STORAGE  
---C1-MAA
- C2-tAA
C3-MAA 
1.4
0	 2	 4	 6	 8	 10	 12	 14	 16	 18	 20	 22 
TIME, me 
Fig. 1. Cell voltage vs storage time, cell series C1-AA, C2-AA, C3-AA, C1-MAA, C2-MAA, and C3-MAA 
JPL TECHNICAL MEMORANDUM 33-418
FSC-PFI 
NSNV
\\\
2.0 
1.8 
1.6 
>
1.4 
0 
> 2.0 
lasted an additional 4.5 mo after the 20-mo storage and 
achieved over 80 cycles before shorting. The total life of 
the cells was 31 mo at room ambient temperature. 
Good results were also obtained on some of the cells 
containing the C19-300 separator material, as shown in 
Figs. 6 and 7. As previously noted, their capacity loss 
was greater, but the cells lasted 30 mo and produced 80 
or more cycles in some instances. The unexplainable 
feature is that, in the case of the 13Y-cell series, it was 
the sterilized (S) cells that survived the test, whereas in 
the case of the 9Y cell series, it was a control (C) cell 
that survived the test, as might be expected. 
The sterilized HMW cells did not perform well, as 
shown in Fig. 8. They neither lasted nor cycled as long as 
the cells with MAA and C19-300 separators. They also 
had a permanent capacity loss of approximately 50% 
after storage. 
The open-circuit voltage curves of the cells in storage 
indicated that, once the cell voltage dropped from 
the upper-voltage plateau, it was difficult to predict the 
future performance of the cell. The voltage of seven
of the cells dropped from the upper-voltage plateau and 
continued to drop without pausing at the lower 1.58-V 
plateau, while the voltage of nine of the cells dropped 
to the lower-voltage plateau and remained there for 
several months. The data also indicated that, once the 
cell voltage dropped below 1.58 V, the cell was shorted 
and no energy could, be obtained from it, as shown by 
cells C2-AA and HMW-2PF in Figs. 1 and 4, respectively. 
All cells with an open-circuit voltage above 1.58 V 
produced some usable energy. 
Unfortunately, the test did not include control cells 
containing FSC or cellophane separators. 
An expanded test program to evaluate cells was 
recently initiated by JPL. Basically, the program will 
investigate the shelf and cycle life of cells with different 
separator systems at several different temperatures. 
V. Conclusions 
Sterilized and unsterilized control silver—zinc cells 
were subjected to an extended shelf life test at room 
ambient temperature followed by a cycle life test. 
U
- - -	
- 
---CELL 1% AA  
CELL 2% AA 
0	 2	 4	 6	 8	 10	 12	 14	 16	 18
TIME, mo 
Fig. 2. Cell voltage vs storage time, cell series NSNV, FSC-PF1, 1 % AA, and 2% AA 
4	 JPL TECHNICAL MEMORANDUM 33-418 
1.8 
1.6 
1.4
I	 I	 I	 I	 I	 I 
ON APRIL 28, 1965, CELLS 13Y-1C AND 13Y-45 WERE DISCHARGED AND RECHARGED; CELL 
13Y-IC = 33.8 A-h AND CELL 13Y-45 = 17.8 A-h. CELL 13Y-1C SHORTED DURING RECHARGE 
CELL I 
SERIES	 CAPACITY 
--- 13Y-1C 
.......
	
= 15.0 A-h 
- 13Y-3S = 9.0 A-h 
13Y-4S = 13.0 A-h
2.0 
1.8 
1.6 
> 
(5
1.4 
24 
The voltage of 6 of the 28 cells remained on the upper-
voltage plateau for 12-20 mo. Upon discharge following 
the storage period, only the MAA cells delivered capaci-
ties comparable to their initial capacities. After a second 
storage period of 4.5 mo, the cells delivered 80 cycles 
without shorting. Good results were also obtained from 
some of the cells containing C19-800 separators; however, 
the results were not as consistent as with the MAA 
separators, and cell capacity loss during storage was 
much greater.
The open-circuit voltage cannot be used to predict the 
capacity of a given cell; if the open-circuit voltage drops 
below 1.58 V, shorting of the cell can be predicted. 
Future planetary probes will require batteries with 
long shelf life and recharge capabilities. Based upon the 
results of the data presented in this report, it is concluded 
that additional research should be done with the MAA 
separator material. 
CELL 
SERIES	 CAPACITY 
1.6	
---9Y-1C = 20A-h 
I	 I
	 9Y-2C = 24A-h 
I	 - 9Y-4S 
1.4
0	 2	 4	 6	 8	 10	 12	 14	 16	 18	 20	 22 
TIME, mo 
Fig. 3. Cell voltage vs storage time, cell series 13Y-1C, 13Y-2C, 
13Y-3S, 13Y-4S, 9Y-1C, 9Y-2C, 9Y-3S, and 9Y-4S 
U
1.8
JPL TECHNICAL MEMORANDUM 33-418 	 5 
2.0 
1 .0 
1.6 
> 
< 1.4 
2.0 
0
1.6 
-.----.-
.
- \\ 
CELL I	 \ 
SERIES	 CAPACITY \	 \\ 
- --- 9PF-1 = 0 A-h  
9PF-2 = OA-h 
- 9PF-3= OA-h \
\
\
\ 
CELL  
SERIES	 CAPACITY  
HMW-2PF =
	 0 
HMW-4	 = 6.5 
- HMW-5 = 4.5
A-h 
A-h 
A-h
....... 
1.4         
0	 2	 4	 6	 8	 10	 12	 14	 16	 18
TIME, mo 
Fig. 4. Cell voltage vs storage time, cell series 9PF-1. 9PF-2, 9PF-3, HMW-2PF, HMW-4, and HMW-5 
40 
30 
20 
4 
4 0
10 
0
I	 I I
j = IC1-MAA C2 - MAA 
X =	 C3-MAA 
C3-X JI Q =	 CYCLE NUMBER 
I 0 J 0 I C3-MAA	 J	 I® ©
I 
- I
II- 
STORAGE	 STORAGE
I 
STORAGE	 STORAGE	 STORAGE	 I 
12 days	 30 days I 14 m	 6 m	 4.5mo Cl -wA SHORTED 
C2-MAA SHORTED
'0	 '0	 '0	 '0
 
DATE 
Fig. 5. Capacity as a function of storage time and cycle, cell series Cl -MAA, C2-MAA, and C3-MAA 
6	 JPL TECHNICAL MEMORANDUM 33-418 
J = C-CELLS 
=S-CELLS 
Q = CYCLE NUMBER 
) I	 9Y-1C EXPLODED ON 15th CHARGE I	
£ 
'I	
I® 
I	 I 
II	 I
TOTAL LIFE 2.5 yr 
DATE 
Fig. 6. Capacity as a function of storage time and cycle, cell series 9Y-1C, 9Y-2C, 9Y-3S, and 9Y-4S 
60 
-10 -1 
40 
30 0 
0
20 
10 
0
-
CELL REMOVED
FROM TEST 
JPL TECHNICAL MEMORANDUM 33-418 	 7
50
= C—CELLS I	
= S—CELLS 0 0 = CYCLE NUMBER 
60 
20 
10
0 
I	 I
- 
	
STORAGE	 STORAGE	 I I STORAGE 
	
10 days	 19.5mo	 I	 4.5 M0 
	
I	 13Y-1C	 13Y-2C	 13Y-35 
	
I	
SHORTED -
	 SHORTED	 SHORTED
40 
30 
X	 ©	 DISCONTINUED 
x 
-	 "	 -	 - 
-
DATE 
Fig. 7. Capacity as a function of storage time and cycle, cell series 13Y-1C, 13Y-2C, 13Y-3S, and 13Y-4S 
8	 JPL TECHNICAL MEMORANDUM 33-478
CAPACITY BEFORE STERILIZATION 
X 0 x ®
x X = HMW - 2FF 
Ø	
X IHMW-4 
x HMW-5 
$ Q = CYCLE NUMBER 
I 
10-	 I	 I 
I	 I 
I	 I 
I	 I 
I	 I 
I	 I	 I 0 
'0	 I I	 I I	 I	 I ®II •' I	 I	 I •• S.	 • 
I	 I 
STORAGE	 STORAGE 1 STORAGE 
10 days	 I	 16 m I 4.5mo	 • 
0-	 •* so 
STORAGE 
30 days 1 I i
I
I	
HMW-5	 I	
SHORTED I	 -	
- 
SHORTED AT 0 A-h	 SHORTEDI	 ON CHARGE
 
I	 I 
01	 I	 I	 I	 II	 I	 -	 - 
U
-o	
-0 
a, a, 
th
DATE 
Fig. 8. Capacity as a function of storage time and cycle, cell series HMW-2PF, HMW-4, and HMW-5 
References 
1. Bogner, R. S., Heat Sterilizable Silver—Zinc Battery Investigation, Final Report, 
Delco—Remy Division, General Motors Corp., Anderson, Ind., Mar. 15, 1965. 
[Also appears in NASA Accession No. N65-27367 (15218).] 
2. Bogner, R. S., Report of an Evaluation of Delco—Remy Design of Sealed, 
Secondary, Silver—Zinc Electrolytic Cells for Heat Sterilization, Delco—Remy 
Division, General Motors Corp., Anderson, Ind., June 10, 1962. 
3. Wylie, G. M., "Sealed Zinc Silver Oxide Secondary Battery for Surveyor," paper 
presented at Nineteenth Annual Power Sources Conference, Atlantic City, N.J., 
May 18-20,1965. 
JPL TECHNICAL MEMORANDUM 33-418 	 9 


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