OTS PRICE by MikeJenny

VIEWS: 4 PAGES: 25

									                      Second Quarterly Report




      CHA RACTE RIZ ATION O F NICKEL - CADMIUM E L E CT RODE S

                   1 October, 1963 - 1 January, 1964


                       Contract No. NAS5    - 3477




                              Prepared by

                      General Electric Company

                  Advanced Technology Laboratories
                       Schenectady, New Y o r k




                                   for


                       Goddard Space Flight Center
                          Greenbelt, Maryland
    --- -----------
I

          OTS PRICE
I



    - - - -- - - - - - - -
I
                           for

fi%
-
CHARACTERIZATION O F NICKEL-CADMIUM ELECTROD-

            1 October, 1963 - 1 January, 1964




                       Prepared by
       / b 6 d 2 9 ~
                General Electric Cqmpany
                                  2




                            for


                Goddard Space Flight Center
                   Greenbelt, Maryland
SUMMARY
  r6   7 3
     The objective of this contract is to develop a method of analysis and
characterization of the electrodes used i n nickel-cadmium sealed cells. It
is based primarily on a comparison of detailed polarization measurements
of single electrodes before and after periodic operation in selected modes
of cyclic testing of cells at three temperature levels Oo, 25O, and 50' C.
A correlation of this data should provide a basis f o r specifying improved
cells f o r space applications a s well a s comparing c e l l s f r o m various manu
facture rs.
        During the second quarter, the construction of the control and cyclic
testing equipment required f o r the program was completed, and the equip-
ment was checked out and debugged. Electrodes f o r the program were
electrochemically cleaned, weighed, and stamped with identification num-
b e r s . Two batches of electrodes were put through the initial characteriza-
tion t e s t s and one cell was put on cyclic testing to investigate memory ef-
fects. The s t a r t of the remaining two sets of cyclic tests w a s delayed by
modifications required in some of the control equipment and t h e iieed i o in-
vestigate the cause of positive electrode blistering when characterized at
charge and discharge r a t e s of 1. 0 amperes (nominal 1C r a t e ) . &tZA-




                                         ii
                         TABLE O F CONTENTS
                                                               Page
SUMMARY    ..........................                                  ii

LIST O F ILLUSTRATIONS    ...................                          iii

LIST O F TABLES . . . . . . . . . . . . . . . . . . . . . . .          iV

1.0    INTRODUCTION . . . . . . . . . . . . . . . . . . . . . .         1

2.0    DISCUSSION . . . . . . . . . . . . . . . . . . . . . .           4

           Control and Recording Equipment . . . . . . . . . . .        4
                             ................
           Test Cell Assemblies                                         4
                              ...............
           Electrode Preparation.                                       4
           CA-CB Tests   ....................                           5
           C-CTests.     ....................                           8
           RA and RB Tests ...................                          0
                                                                        0



3.0    PROGRAM FORNEXT QUARTER.           . ..........
                                            ?,                          9

4.0    NEW TECHNOLOGY REPORT           ...............                 10

APPENDIX I - C o n t r d . Equipment Schematics . . . . . . . . . .   1-1

APPENDIX I1 . Weight Tabulation of Electrodes . . . . . . . . .       11-1




                                    fii
                             LIST O F ILLUSTRATIONS


    No.                                                                        Page

     1    Typical Characterization Test Curves         . . . . . . . . . . .    6
I


     2    Positive Electrode Blistering       . . . . . . . . . . . . . . .     7




                                LIST O F TABLES


     I    Fi-ogram Tasks .....................                                  ir
                                                                                c)




    I1    Test Cell Summary . . . . . . . . . . . . . . . . . . .               3




                                          .   .   iv
1.0   INTRODUCTION

     This report covers the work done during the second quarter of an 18
month program t o develop a method f o r the analysis and characterization of
the electrodes used in nickel-cadmium spacecraft batteries,

        The goal of the program is to develop a correlation between detailed
characterization data obtained on single electrodes and the behavior of these
electrodes in cells in various modes of cyclic operation. Such a correlation
w i l l provide a basis for specifying improved cells f o r space application and
comparing cells f r o m various manufacturers.

    A breakdown of the program into tasks is given in Table I. The f i r s t
three tasks a r e of a preparative nature. Tasks IV through VI1 constitute the
experimental portion of the t e s t program.

        The t e s t program is divided into two parts: one, the initial characteri-
zation testing of plates (Task IV); and the other, the cycling of cells made
f r o m characterized plates ir? selected modes of operation (Tasks V - VII).
Periodically test cells will be removed from t e s t s and the individual elec-
trodes will be recharacterized and examined f o r changes in physical proper-
t i e s and comparisons made t o the original characterization data.

     The initial characterization w i l l be made by analysis of data taken in
single electrode experiments based on the use of continuous recording of
charge-discharge curves under various testing regimes. The characteri-
zation information w i l l include: 1) polarization of each electrode under
various conditions, 2) complete charge and discharge c u r v e s showing elec-
trode capacity, impurity levels, onset of gassing, graphitic and antipolar
capacity, and reproducibility of cell operation, and 3) the onset of changes
in capacity under various operating conditions.

     A l l plates in the program w i l l be SAFT type VO, prepared a s for space
cells. T e s t s will be made at three temperatures: Oo, 25O, and 50' C. a s
listed in Table 11. Failure analysis on cycled cells w i l l be made, using
visual, mechanical, chemic a1 and elect roc hemic a1 procedure s o

     During the second quarter construction of the control and testing equip-
ment f o r the characterization and cycling t e s t s was completed and operation
of the equipment was checked out. Sufficient eiectrodes f o r use in tne test
program w e r e electrochemically cleaned, weighed and identified a s described
under T a s k 1 1 In addition a total of 2 0 plates were characterized a s p e r
               1.
TaskIV and the shallow cyclingtests (Task V ) were started a t 2 5 O C.




                                         1
                                      TABLE I
                                   PROGRAM TASKS
                                     NAS5 - 3477

                TASK                                         MEASUREMENTS
I      Control and Recording Equipment               None.
         Design and fabrication of
        test equipment.

I1     Test Cell Assemblies                          None.
         Design and fabrication of
         t e s t cells.

I11    Electrode Preparation                         Capacity check and weight.
         E le c t r oc hemic a1 cleaning of
         reference and cell electrodes,
         inspection and welding of
         identification tabs.

1
;'     C'iiaieaciei-lzation Tests - CA         C-A
       and CB
          C -A Constant current
          charging at C / 10, C / 5 and C
                                                     Determine r a t e of 0 2
         C - B C onst ant c u r r e n t              recombination.
         discharging at C/lO, C / 5
         and C                                 C-B   Determine discharge curve.

V      Shallow Discharge Cycling               c-c   Make periodic capacity
       T e s t s C-C                                 determination.
                                                     Make analysis of physical
       Constant current cycling to 25- 3570
                                                     properties.
       range t o determine memory effects
                                                     Recovery test.
VI     Random Discharge T e s t s R-A          R-A   Periodic charge and discharge
                                                     curve.
       Random discharges averaging
       1070, 2570, 50% and 7570 depth of             Recharacterization tests.
       discharge over a 6-day period
       using Gaussian and rectangular
       distribution f o r discharge periods.

v I1   Constant Voltage, Current Limi-         R-B   Periodic charge and discharge
       ted Charging Cycling T e s t s R - B          curve.

       Charge at C / 5 r a t e and discharge
       at c/2 r a t e t o 0. 9 volts.                Re c har act e ri z at ion t e s t s .
                                               2
                                    TABLE I1

                            TEST CELL SUMMARY


                          Temperature       Total            Plates/CeU
       Test         o°C      25OC    5OoC C e l l s   Ni      Cd   Ni     C d Ref.
                                                           Test         Counter
CA-CB
 Characterization    8        8         8      24     1       1    2       2    1

 Gassing             2        2         2       6     1       1    2       2    i

  0 2 Recombination 1         1         1       3     2       1    0       0    1

c-c                  3        3         3       9     4       4    0       1    0

R-A                                            18     1       1    0       1    0

                              1         1
                              1         1
                              1         1
                              1         1
                              1         1
                              1         1

R-B                  2        2         2       6     4       4    0       1




                                        3
2. 0 DISCUSSION

     The work performed on each task listed i n Table I is reported in the
following sections.

2 . 1 Control and Recording Equipment          - Task I
    The construction of the control equipment f o r conducting the CA-CB,
C-C, R-A, and R-B t e s t s was completed. The circuit schematics f o r these
may be found in Appendix I of the f i r s t quarterly report.

     Several problems were encountered i n the CA-CB equipment which de-
layed the s t a r t of the characterization tests. Some of the Rustrak Recorders
used to r e c o r d the potential of the nickel and cadmium electrodes v e r s u s the
reference electrode yielded e r r a t i c voltage readings. Apparently this was
caused by ground loop potentials, existing between control panel c i r c u i t s and
the r e c o r d e r amplifier chassis. Not all of the r e c o r d e r s behaved in this
fashion when installed in the eqilinmeat czbinetc. Calibration nf these units
                                      -*r-
removed f r o m the cabinets showed them to be satisfactory, The problem
was resolved by selecting amplifier units from stock that gave c o r r e c t read-
ings when installed in the cabinets.

        The other problem involved a design e r r o r which tied the reference elec-
t r o d e s in the nickel and cadmium characterization t e s t c e l l s to a common
e l e c t r i c a l connection. Since the two t e s t cells a r e connected in parallel to
the charge and discharge power supply, connecting the reference electrodes
together allowed them t o discharge against the cadmium electrodes. The
c i r c u i t s w e r e modified to break the common connection and switch the r e f e r -
ence electrodes by means of additional relays actuated by the control timer.
A revised circuit diagram showing these modifications may be found i n Ap-
pendix I.

2. 2 T e s t Cell Assemblies   - Task I1
     No work was scheduled on this task f o r this quarter. The design and
construction of the special t e s t cells f o r determining gassing and recombina-
tion r a t e s w i l l be undertaken during the third quarter.

2. 3 Electrode Preparation - Task I11

     Approximately 6 0 0 electrodes were electrochemically cleaned by the
procedure described in Table I1 of the first quarterly report. Electrodes
rejected on the basis of visual defects were l e s s than one percent.

    The final weights of the electrodes after cleaning a r e tabulated i n Ap-
pendix 11. These w i l l be reweighed prior to characterization t o provide a
reference point f o r comparison after the electrodes a r e removed f r o m the
                                           4
various cyclic t e s t s . The average weight of the positive elements a f t e r
cleaning w a s 11. 150 gms with a standard deviation of 0. 290 gms, and f o r
the negative electrodes the average was 10.161 gms with a standard devia-
tion of 0. 259 gms. Weight changes for the positive electrodes before and
after cleaning averaged -f 0.028 gms; for the negatives the weight decreased
on the average of 0. 273 g m s .

2.4 C A - C B T e s t s   -   T a s k IV

       Two batches of electrodes (10 positives and 1 0 negatives p e r batch)
were characterized at nominal C / 5 and C r a t e s , at room temperature (ap-
proximately 25O C. ). The cycle conditions f o r the C / 5 r a t e t e s t s were,
charge f o r 360 minutes and discharge f o r 300 minutes at 0. 2 8 amp. F o r
the C r a t e t e s t s , the conditions were charge f o r 1 0 1 minutes and discharge
f o r 84 minutes at 1. 0 amp. In both c a s e s the charging time was approxi-
mately 12070 of the discharge time,

        A l l plates were given seven consecutive complete charge and discharges.
Potential time curves for each electrode versus a fully charged and aged
nickel reference electrode were continuously recorded for the seven cycles.
The potential time curves at the C / 5 r a t e f o r both positive and negative elec-
t r o d e s w e r e observed t o be normal with respect t o the general shapes of the
curves and c h a r a c t e r i s t i c points of inflection at various stages i n the charge-
discharge cycle. The types of curves observed a r e shown i n Figure 1.

         The most noticeable trends observed over these initial cycles were: f o r
the nickel electrode, a progressive increase i n the length of the graphite s t e p
i n the discharge portion of the cycles; for the cadmium electrode, a progres-
sive d e c r e a s e in time at which the inversion point was obtained. T h i s behavior
is not unusual and has been observed i n previous experiments. The full sig-
nificance of these changes and interpretation must await the r e s u l t s of studies
which w i l l be made on the electrodes after removal f r o m the various cycling
t e s t s l a t e r i n the program.

     The nickel electrodes characterized at the C r a t e were observed t o
develop b l i s t e r s on both s u r f a c e s in which the sintered nickel m a t r i x was
separated f r o m the nickel-plated sheet of the electrode. Examples of this
phenomenon a r e shown i n the photograph of Figure 2. Nine out of ten of the
nickel electrodes in the batch showed blisters ranging f r o m approximately
1/ 8 t o 1/ 2 in. in diameter.

     Supporting studies a r e being undertaken t o determine if the phenomenon
is the r e s u l t of a defective lot of electrodes o r whether the electrode is being
subjected t o gassing conditions which cannot be accommodated by the elec-
trode s t r u c t u r e .

     A check with the Battery Product Section a t Gainesville, Florida, was
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                      6
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        made with respect t o history of this lot. There w a s no history of manufac-
        turing problems at the time the plaques were made. However, the electrodes
        had not been used i n any cells and therefore t h e r e was no comparative infor-
        mation a s t o their performance in cells, A l e s s s e v e r e c a s e of this phenomenon
        has been observed at Gainesville when nickel electrodes were r u n i n the inverted
        conditions at r a t e s of approximately C / 8 to C / 5 f o r periods of twenty t o twenty-
        four hours. It maybe that at the C r a t e the phenomenon may be m o r e s e v e r e
    I   i n a short period of time. The time that the electrodes were in the inversion
    ~
        mode i n the cycle used was approximately 15 minutes. In addition, an exami-
        nation of the potential t i m e curve shows an inflection point for the nickel elec-
        trode p r i o r t o the end charge which is an indication of heavy gassing. Such
        an inflection was not observed f o r the electrodes r u n at C / l O or C / 5 r a t e s .
        Thus it may well be that the combined gassing on charge and on over-discharge
        may both be contributing to the blistering.

I
                 Pending the r e s u l t s of the supporting studies which will be completed in
I
I       the third quarter, i t is planned to r e s t r i c t all future initial characterization
        t e s t s to the C / l O r a t e .

        2 . 5 C-C T e a t s - Task V

I             These tests a r e designed t o determine the onset and severity of memory
        effects. T e s t cells consisting of five cadmium and four nickel electrodes
        p e r cell will be cycled at constant current simulating the conditions of a 90
        minute orbit, 35 minute discharge and 55 minute charge. The depth of d i s -
        charge w i l l be limited t o 25%.

             One c e l l was put on t e s t during the quarter. It is planned t o cycle this
        one f o r 500 t o 600 cycles and then check one pair of electrodes for capacity
        using fully charged counter electrodes to 0. 9 volt at the cycling discharge
        rate, followed by discharge through a resistor to z e r o voltage. This w i l l
        check the capacity of the plate and determine which plate is showing the
        memory effect and the severity of the effect.

             If memory has set in, a t e s t plate will be removed without discharge
        and examined by physical methods (X-ray diffraction, etc. ) to determine
        what changes if any have occurred. The remaining plates w i l l be electrochem-
        ically tested to determine recovery from memory and recharacterized plates
        will be replaced i n the cycling t o accumulate data.



             The problems encountered in the previous t a s k s delayed the s t a r t of
        these t e s t s . The testing equipment required, as indicated e a r l i e r , is @om-
        pleted and available f o r use.

               During the next q u a r t e r a s a sufficient number of plates a r e accumulated
        f r o m the initial characterization t e s t s , c e l l s will be put on cyclic testing a s
        described i n the f i r s t quarterly report.
                                                         8
I   3.0   PROGRAM FOR NEXT QUARTER
I
i            The characterization t e s t C A - C B f o r electrodes to be used i n the cyclic
    t e s t s w i l l continue using the C / l O r a t e s (-0. 1 amp. ) f o r a l l electrodes.
    Supporting studies on the blistering problem w i l l be conducted to determine
    the cause of this phenomenon.
~




           A s electrodes a r e accumulated f r o m the C A - C B t e s t s , cells will be put
    on cyclic testing. The r a t e at which these t e s t s can be gotten underway w i l l
    be slower than originally scheduled since more time w i l l be required f o r the
    characterization at the C / 1 0 rate. The characterization time at this r a t e is
    approximately 4 1 / 2 days p e r batch of 1 0 positives and 1 0 negatives, allowing
    f o r setup time f o r each batch,

            These changes will reduce the total number of cyclic t e s t data that can
    be accumulated on each task. However, it will not affect the achievement of
    the overall program objectives; namely, to identify the importance of the
    f a c t o r s being investigated in each task.




                                                  9
    4.0 NEW TECHNO-LOGY REPORT

         T h e r e were no new developments during this quarter which come under
,
~




    the “New Technology” clause of t h i s contract.




                                        10
        APPENDIX I


Control E quipment Schematics




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   4
                                              PARTS LIST
                                                                                    Part 2 of 2 Parts

 P-1 Line C o r d , CA-CB C o n t r o l l e r

 P - 2 Control, C h a r g e , Pin J a c k s , Yellow

 P - 3 Control, D i s c h a r g e , Pin Jacks, Red

P - 4 Input C h a r g e , CCS, Terminal

P - 5 Input D i s c h a r g e , CCS Terminal

P-6 t h r u P-15        Pin J a c k s , C e l l Input Red t, G r e e n     +,   White R, Blue -, B l a c k   -
P-16 t h r u P - 1 7 Pin J a c k s R e c o r d e r , R e d + , B l a c k   -
P-18 Pin J a c k s , G. R. for R L

SW Switch, Toggle SPDT

F Fuse, 3A

PL-1 Pilot, M a s t e r , G r e e n

P L - 2 Pilot, C h a r g e , Yellow

P L - 3 Pilot, D i s c h a r g e , Red

T Timer, CM, 2 Min

R L L o a d R e s i s t a n c e (See Drawing)

K-1, K-2       M e r c u r y Relax, 3PST 2N0, lNC, Ebert EM7, 110 VAC C o i l

K-3, K-4 L e a c h 329-7 4PDT, 110 VAC Coil

K-5, K-7, K-8 L e a c h 337 2PDT, 1 1 0 VAC C o i l

S-1 t h r u S-10 Switch SPST Toggle "Bias1'

B-1 t h r u B-10 Battery M e r c u r y 0 C e l l

R - 1 t h r u R-10,     50,000    a 2 Watt
R - l l t h r u R-20,    3 Meg


                                                  I- 3
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