A method of fabricating a rechargeable battery is disclosed which includes a positive electrode which contains a chloride of a selected metal when the electrode is in its active state. The improvement comprises fabricating the positive electrode by: providing a porous matrix composed of a metal; providing a solution of the chloride of the selected metal; and impregnating the matrix with the chloride from the solution

Bankston, C. Perry

Bugga, Ratnakumar V.

Distefano, Salvador

English

NASA Technical Reports Server

United States Patent [ii]  Patent Number: 5,019,470 
Bugga et al. [45] Date of Patent: May 28, 1991 
[54] METAL CHLORIDE CATHODE FOR A 
BATTERY 
[75] Inventors: Ratnakumar V. Bugga, Arcadia; 
Salvador DiStefano, Alhambre; C. 
Perry Bankston, Studio City, all of 
Calif. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 503,409 
[22] Filed: Mar. 30,1990 I 
[51] Int. C l . 5  ........................ HOlM 4/58; HOlM 4/04 
[52] U.S. Cl. .................................... 429/223, 29/623.5 
[58] Field of Search ........................ 429/223; 29/623.5 
[561 References Cited 
US. PATENT DOCUMENTS 
3,959,012 5/1976 Liang et al. ..................... 429/223 X 
4,508,799 4,4983 Gopikanth et al. ............. 429/223 X 
4,529,676 7/1985 Galloway et al. .............. 429/223 X 
4,626,483 12/1986 Bones et al. .................... 429/103 X 
Primary Examiner-Stephen J. Kalafut 
Attorney, Agent, or Finn-Thomas H. Jones; Harold W. 
Adams; John R. Manning 
[571 ABSTRACX 
In a method of fabricating a rechargeable battery which 
includes a positive electrode which contains a chloride 
of a selected metal when the electrode is in its active 
state, the improvement comprising fabricating the posi- 
tive electrode by: providing a porous matrix composed 
of a metal; providing a solution of the chloride of the 
selected metal; and impregnating the matrix with the 
chloride from the solution. 
14 Claims, 1 Drawing Sheet 
............................................... ..................... .... ... 2600} . .. 
I '  / ' *  
VOLTAGE, E(MV) 
I I I I 
2000b 1800 3600 5400 7200 
TIME, SEC. 
https://ntrs.nasa.gov/search.jsp?R=19910018164 2020-03-24T07:00:20+00:00Z
U.S. Patent 
2200- 
May 28, 1991 
I I I * 
5,019,470 
I FIG 1 
26001 ................ ................ ............................... ... .......... . 
j * e . .  a a /'.. 
2 a I .  . . 
VOLTAGE, E(WV) 
FIG 2 
TIME, SEC. 
5,O 19,470 
CI 1 
METAL CHLORIDE CATHODE FOR A BA"'JlRY 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract, and is sub- 
ject to the provisions of Public Law 96-517 (35 U.S.C. 
202) in which the Contractor has elected not to retain 
5 
title. 
TECHNICAL FIELD 
The present invention relates to rechargeable batter- 
ies, and particularly batteries having a metal chloride 
cathode. 
BACKGROUND OF THE INVENTION 
Batteries, such as sodium batteries, having a metal 
chloride cathode are known to constitute useful re- 
chargeable energy sources having high energy and 
power density properties. While sodium-sulfur batteries 
have proven useful, they have been found to have cer- 
tain shortcomings. 
In particular, known sodium-sulfur batteries experi- 
ence significant corrosion problems, due to higher oper- 
ating temperatures, and present safety hazards Sodium- 
sulfur batteries also suffer from degradation of solid 
electrolytes in polysulfide melts. 
Recently, sodium batteries with metal chloride cath- 
odes have attracted interest because they appear to offer 
energy densities comparable to those of' sodium-sulfur 
batteries, but are less subject to the abovedescribed 
drawbacks. Energy density is here defined as the open- 
circuit voltage of the battery multiplied by its coulom- 
10 
15 
20 
25 
30 
bic capacity% ampere-hours, divided by the weight of 35 
the electrodes. 
Among the various metal chlorides which have been 
investigated for use as cathodes, nickel chloride has 
been found to be worth considering because it provides 4o 
an energy density higher than that of ferrous chloride 
and presents a good resistance to overcharge. 
Various approaches to the fabrication of the positive 
electrode, or cathode, of such a battery have included: 
producing a porous metal body by sintering a metal 45 
powder in a reduced atmosphere and then chlorinating 
the metal body; impregnating a metal matrix with a 
brine solution of sodium chloride and assembling the 
battery in the discharged state; sintering a mixture of 
metal powders and a slurry of sodium chloride in brine; 50 
and sintering dry powders of metal and sodium chlo- 
ride. Subsequent to fabrication, the electrode must be 
converted to active form electrochemically to form 
NiC12. 
of steps. Moreover, particularly if the electrode is 
formed by sintering metal powder and sodium chloride 
together, the resulting electrode may not exhibit great 
mechanical strength. Therefore, the electrode is subject 
to failure due to mechanical stresses induced therein 60 
during successive charging and discharging cycles. 
Thus, formation of such an electrode entails a number 55 
STATEMENT OF THE INVENTION 
It is an object of the invention to provide an im- 
proved positive electrode for such rechargeable batter- 65 
ies. 
Another object of the invention is to provide an im- 
proved method for fabricating such positive electrode. 
L 
A more specific object of the invention is to simplify 
the fabrication of a metal chloride cathode electrode for 
a rechargeable battery. 
A further specific object of the invention is to in- 
crease the mechanical strength, and particularly the 
stress resistance of such positive electrodes to improve 
cyclability as demonstrated by the adoption of similar 
technique for the fabrication of electrodes in other aero- 
space batteries. 
The above and other objects are achieved, according 
to the invention in a method of fabricating a recharge- 
able battery which includes a positive electrode which 
contains a chloride of a selected metal when the elec- 
trode is in its active state, by fabricating the positive 
electrode by: providing a porous matrix composed of a 
metal which is at least as noble as the selected metal; 
providing a solution of the chloride of the selected 
metal; and impregnating the matrix with the chloride of 
the selected metal from the solution. 
The objects according to the invention are further 
achieved by the provision of a rechargeable battery 
having a positive electrode fabricated in the manner 
described above. 
Batteries constructed with a positive electrode ac- 
cording to the invention can be used to advantage in 
spacecraft, electric vehicles, military vehicles and other 
applications where a high energy density power source 
is desired. 
The metal of the matrix may be the selected metal. 
However, improved results will be achieved if the metal 
of the matrix is nobler than the selected metal. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a diagram illustrating the discharge behav- 
ior at different rates of an NiCl2-Na battery having a 
positive electrode according to the invention. 
FIG. 2 is a diagram illustrating the performance of 
the same battery during selected charge and discharge 
DETAILED DESCRIPTION OF THE 
INVENTION 
The invention is applicable to any battery having a 
cathode, in batteries the cathode being the positive 
electrode, made of NiClz or a chloride of any suitable 
metal, such as Fe, Cu, etc., and an anode, or negative 
electrode, of sodium, lithium, or other alkali or alkaline 
earth metals. There presently appears to be a preference 
in the art for NiC12 cathodes, for reasons mentioned 
earlier herein, and sodium or lithium anodes. 
The electrolyte of such a battery is selected, on the 
basis of known principles, to have a composition com- 
patible with the electrodes. One electrolyte system to 
which the invention may be advantageously applied is 
composed of beta alumina solid electrolyte and 
NaAlCl4, preferably in conjunction with sodium and 
NiC12 electrodes. 
According to a preferred embodiment of the inven- 
tion, the electrode is constituted essentially by a nickel 
matrix impregnated with nickel chloride. The nickel 
matrix may be a sintered nickel plaque of a type which 
is commercially available and is used in Ni-Cd batteries. 
Chloride is introduced into the matrix from a saturated 
nickel chloride solution. 
The nickel chloride constitutes the active material of 
the cathode and higher loadings in the matrix can be 
achieved by using techniques such as vacuum impreg- 
nation, etc. 
periods. 
5,019,470 
3 
It may additionally be beneficial to subject the nickel 
matrix to pretreatments of the type performed on NiCd 
batteries, such as preoxidation. 
Because the impregnated material is already in the 
form of metal chloride, subsequent steps to activate the 
electrode are not required. 
The materials constituting the matrix and the impreg- 
nating solution need not be specially purified and bat- 
tery grade nickel and nickel chloride have been found 
to produce good results. In more general terms, any 
metals known to be suitable for a battery cathode can be 
used for the matrix and the chloride. 
A positive electrode according to the invention was 
fabricated by chemically impregnating a nickel plaque 
body with nickel chloride from its saturated solution to 
a loading of 4 mAh/cm2. Higher loadings should be 
possible if optimum conditions and improved impregna- 
tion methods are employed. The electrode was then 
dried overnight at 150' C. The electrode had an area of 
4 cm2, and thus a total loading of 16 mAh. The elec- 
trode was part of a N a h t a  battery, the electrode was 
found to have high columbic yields of above 95%, 
based on the amount of NiC12 impregnated, at high 
current densities greater than 8 mA/cm2. The discharge 
of a battery equipped with this electrode is depicted in 
FIG. 1 in terms of the variation in battery voltage with 
time for three discharge current levels. 
Curve 1 of FIG. 1 corresponds to a discharge current 
of 8 mA, curve 2 a discharge current of 16 mA and 
curve 3 a discharge current of 32 mA. 
Moreover, the battery experienced no detectable loss 
in capacity as a result of charge/discharge cycling, 
implying a high degree of integrity of the positive elec- 
trode This is illustrated in FIG. 2, which shows the 
variation of the battery voltage with time during suc- 
cessive discharges and during one charge, at a tempera- 
ture of 200' C., and with a current in each case of 8 mA. 
Curves 11, 12 and 13 represent the battery voltage 
variation during the second, third and fourth dis- 
charges, respectively, while curve 14 represents the 
battery voltage variation during the second charge. The 
voltage variation during the first discharge is shown by 
curve 1 of FIG. 1. 
While the descriDtion above refers to Darticular em- 
4 
strictive, the scope of the invention being indicated by 
the appended claims, rather than the foregoing descrip- 
tion, and all changes which come within the meaning 
and range of equivalency of the claims are therefore 
5 intended to be embraced therein. 
We claim: 
1. In a method of fabricating a rechargeable battery 
which includes a positive electrode which contains a 
chloride of a selected metal when the electrode is in its 
10 active state, the improvement comprising fabricating 
15 
20 
25 
30 
35 
40 
bodiments of the present invention, it \;ill be under- 45 
stood that many modifications may be made without 
departing from the spirit thereof. The accompanying 
claims are intended to cover such modifications as 
would fall within the true scope and spirit of the present 
invention. 50 
The presently disclosed embodiments are therefore to 
be considered in all  respects as illustrative and not re- 
the positive electrode by: providing a porous mat& 
composed of a metal which is at least as noble as the 
selected metal; providing a solution of the chloride of 
the selected metal; and impregnating the matrix with 
the chloride from the solution. 
2. A method as defined in claim 1 wherein the solu- 
tion provided is a saturated solution of the metal chlo- 
ride. 
3. A method as defined in claim 2 wherein said step of 
impregnating is performed under a vacuum. 
4. A method as defined in claim 3 wherein the porous 
matrix consists essentially of nickel. 
5. A method as defined in claim 4 wherein the porous 
matrix consists essentially of a sintered nickel plaque. 
6. A method as defined in claim 3 wherein the porous 
matrix consists essentially of a metal which is nobler 
than the selected metal. 
7. A method as defined in claim 3 wherein the se- 
lected metal of the chloride is nickel. 
8. A method as defined in claim 3 wherein the metal 
of the porous matrix is the same as the selected metal of 
the chloride. 
9. A method as defined in claim 1 wherein the porous 
matrix consists essentially of nickel. 
10. A method as defined in claim 10 wherein the 
porous matrix consists essentially of a sintered nickel 
plaque. 
11. A method as defined in claim 1 wherein the po- 
rous matrix consists essentially of a metal which is no- 
bler than the selected metal. 
12. A method as defined in claim 1 wherein the se- 
lected metal of the chloride is nickel. 
13. A method as defined in claim 1 wherein the metal 
of the porous matrix is the same as the selected metal of 
the chloride solution. 
14. A rechargeable battery comprising a positive 
electrode fabricated by the method defmed in claim 1, 
said electrode including: the porous matrix of the metal 
which is at least as noble as the selected metal; and the 
chloride of the selected metal present only in the pores 
of the matrix. * * * * *  
55 
65 


Metal chloride cathode for a battery

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