Heat activated emf cells with aluminum anod

Greenberg, J.

English

NASA Technical Reports Server

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ATTN OF. Gp 
A& u.23 
NATIONAL AERONAUTICS AND SPACE AD NIS RATION 
WASHINGTON. D.C. 20546 
usI /Scient i f ic  & Technical Information Division 
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F ROM t ~ ~ / ~ f f i c e  of Assistant  General Counsel f o r  
Patent  Matters 
I 
SUBJECT: Announcement of NASA-Owned U. S. Patents  i n  STAR 
I n  accordance with the  procedures agreed upon by Code GP 
and Code USI, the  attached NASA-owned U. S. Patent is being 
forwarded f o r  abst ract ing and announcement i n  NASA STAR. 
The following information is prwidedt  
U. S. Patent  No. 
Government o r  
Corporate Employee 
Supplementary Corporate 
Source (if  applicable)  t 
NASA Patent  Case No. 
NOTE - I f  
employee 
Pursuant 
t h i s  pa ten t  covers an invention made by a corporate 
of a NASA Contractor,  the  following is applicable: 
yes No @ 
t o  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 ac tua l  
inventor (author) appears a t  t he  heading of Column No. 1 of 
the Specif icat ion,  following the  words a. . . with respect  t o  
Enclosure 
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q (NASA CR OR TMX OR AD NUMBER) 3 
Y (CATEGORY) 
https://ntrs.nasa.gov/search.jsp?R=19710019103 2020-03-17T03:14:25+00:00Z
HEAT 
HEAT ACTIVATED CELL 
Filed Dec. 30, 1968 
HEAT 
FIG. 3 
v -e----- 
HEAT ---3- ---- HEAT 
__)_ rC------ 
-'-!I 
FIG. 4 
INVENTOR 
JACOB GREENBERG 
3,533,986 United States Patent O 6 c e  tea npr. B. 1971 
Jacob Greenberg, Pepper Eke, Ohio, assignanon tap the 
fiiteka States of Ameaiea as  represented by the Ad- 
miIliis&;r;a&or of the Nafional Aeaonnaufies and Space 
Adminlstrafion 
Filed Dee. 30, 1968, Ser. No. 787,911 
h t  el. Holm 21/00.17/06 
cell using an aluminun~ anode. The cell operates at high 
efficiency by using a thin, heated electrolyte canigrising 
at least one aluminum salt. Depending on the materials 
nsed for the cathode and the electrolyte, %be cell may 
be operated with either the electrolyte or ih: cathode 
in a molten state. 
BRIEF DESCRIPTION OF THE DRAVVINGS 
FIG. 1 is a cross-sectional view of one coniQgural;oa 
of a cell embodying the invention; 
FIG. 2 is a cross-sectional view of a cell in which the 
anode, cathode, and electrolvte are in the Earm of side- 
A heat activated electromotive force (EMF) cell hav- by-side plates; 
ing an anode formed of aluminum and a cathode com- FIG. 3 is a pictorial drawing of a rel1aSEe ceE: ern- 
prisii~g an oxidizing material such as sulfur. The cathode 15 bodying the invention; and 
material is supported in a container or in a matrix such FIG. 4 is a cross-sectional view of still another form 
as porous carbon. An aluminum salt layer electrolyte of cell embodying the invention. 
such as AlCl separates the anode from the cathode. To 
minimize vaporization of the aluminum salt, an alkali DESCRIPTION OF Pi FREFERRIED 
halide salt may be mixed therewith. The cell may be 20 EMBODIMENT 
operated at temperatures up to a point where either the Referring now to FIG. 1, it will be seen mat a cd i  
cathode material o r  the electrolyte is molten. constructed in accordance with the invention may includz 
an aluminum container PO which scrves as tire acode of 
the cell. A post 11 formed of porous carbon sslurated 
ORIGIN OF THE MVENTIOW 25 with snrlfur i s  disposed in the container I@ to scxve as a 
This invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government of 
the United States of America for governmental purposes 30 
without the payment of any royalties thereon or therefor. 
B A C K G R O m D  OF THE INVENTION 
This invention relates t o  heat activated EMF cells 
and is directed more particularly to  a heat activated EMF 35 
cell having an aluminum anode. 
Because of its low equivalent weight, relatively high 
energy density, ease of handling, and availability in many 
inexpensive forms, alun~inurn is a very desirable material 
for use as battery anodes. In the past, some EMF cells 40 
have been constructed using aluminum anodes with 
aqueous electrolytes. Such EMF cells have not been suc- 
cessful because of corrosion which occurs of the alumi- 
num anode. This corrosion causes unacceptably low 45 
efficiency in aluminum anode cells. 
Accordingly, it is an object of the invention to provide 
an improved aluminunz anode cell. 
It is another object of the invention to provide an 
aluminum anode cell having high eficiency. 50 Still another object of the invention is to provide an 
aluminum anode cell having a relatively thin ekctrolyte 
of large area. 
A further object of the invention is to provide a heat 
activated, aluminum anode cell which may be operated 55 
at  temperatures at which the electrolyte may be either 
solid or molten. 
An additional object of the invention is to provide an 
EMF cell having an aluminum mode which does not 
corrode. 
It is yet another object of the invention to provide a 60 
cell of the above type in which the cathode may be 
either solid or molten. 
In summary, the invention provides a heat activated 
cathode. The sulfbr must be substantially c0mple:ely and 
evenly distributed in the porous carbon of the poet PI 
in order for the post to function properly as a czthode. 
The porous carbon thus serves as a matrix or Z~older- 
support for the sulfur cathode material. Becaiisc ?lethods 
of saturating porous carbon with sulfkr are w z l  known 
to those skilled in the art, such methods will not be 
described herein. 
If desired, the cathode post 11 may be formed of any 
metal which: may be made in porous form; i s  lower in 
the electromotive series than aluminum; and does not 
react chemically with the sulfur or anjr other seritablc 
cathode materials used to saturate the cal81ode past 11. 
Other suitable materials which may replace the siiBi'ur 
in the post 11 include any O2 or @I producing n3arcrials. 
as for example, halogen compounds or organic corn- 
pounds containing oxygen. In general, the caii~ode may 
be any suitable oxidizing material which will react -~:tk 
aluminum to form an aluminum salt. 
To the end that the cell shown in FIG. 1 will pro- 
duce a relatively high current density at high cficiency. 
a thin electrolyte 12 is disposed between tkle caltPode post 
$1 and the aluminum container 10 and IS henled by 
heat applied to the cell. An electrolyte tbiclc~iess of one- 
eighth inch is sufficieniiy thin for the st~ucture shown 
in FIG. 1. In accordance with the invention, the elec- 
trolyte 12 comprises at  least one aluminum salt. At least 
one alkali halide salt may be added to the aluminuin 
salt to minimize vaporation of the aluminum salt. Bc- 
cause it is generally desirable to operate a heat activated 
cell at the lowest possilble temperature, ancl bccanse of 
considerations of economy, availability, and ease of han- 
dling, a eutectic mixture of AICI-NaCl bas been Fotind to 
be the most suitable electrolyte. With this partrcular 
electrolyte mixture or with any aluminum halid: salt- 
alkali salt mixture, the cell is normally operated in a 
temperature range of from about 50" 45. to aboat iOOo 
nally applied heat. However, the sell may 
3,573,986 
3 
be operated up to temperatures greater than the melting 
4 
A s  current flows between the anode 10 and the elec- 
point of the electrolyte mixture if desired. The upper- trode 17  through the load 18, electrochemical action be- 
most practrcal l~lrnnt is about 600" C., which is well tween the anode 10 and the cathode BI progressas. Alumi- 
beio+~ the r aelling point of the aluminum anode. num ions build up on the anode 10 while sulfide ions build 
The cell of FIG. 1 is completed by a cover plate 13 up on the carbon electrode 17. The sulfide ions accumulat- 
and electrodes 14 and 15. The cover plate 13 is an ing or, the electrode 17 tend to  educe or at least limit 
electrical ~nsulating material such as ceramic. The elec- the current capability or energy density of the cell. How- 
teodes 114 may be either carbon or  any suitable metal ever, the sulfide ions will react with the water in the 
coapz;t~ble with the materials used in the cathode post molten cathode to form H2S. Accordingly, the cell may 
11, the anode 18 and the electrolyte 12. be made to provide a relatively high current output by 
FAG. 2 iilarst~a?es an alternate arrangement of the cell removing the E&S gas which forms at the electrode 17. 
wown In FIG i ~ n d  like parts are identified by like l o  this ~113, thc H,S is allowed to escape through a vent 
~iumes'~ls In FlG. 2, the anode PO, the cathode 11, and 19 provided in the cover plate 15. 
line electrolyte $2 are in the form of side-by-side plates. By making the load 18 a relatively low resistance, a 
The electrolyte 12 IS positioned between the anode 10 15 relatively high current will be transferred between the 
a?d tile cathode 81. A suitable container 16 made of elec- anode PO and the eleclrode 17. This accelerates the elec- 
trically 3oncondcict1ie matelial is disposed around the trochemical action taking place between the anode 10, 
 node 10, tlie catlode 11, and the electrolyte 1 2  to hold the cathode 11, and the electrolyte 12 and produces heat- 
-hem in place. ing. Thus, by selecting a load 18 of sufficiently low re- 
FIG. 3 plilor~ally shows another possible arrangement 20 sistance, enough heat may be generated in the cell to 
of d c:l? constiucied in accordance with the invention. make its operation self-sustaining. Consequently, it will 
Parts In FIG. 3 are identified by numerals corresponding be seen that, with a properly selected load 18, the ex- 
io bike patts In FIGS. 1 and 2. In the cell of FIG. 3, the terior heat applied lo the cell to initiate operation may 
anode 10 ii LL sheet of aluminum foil. The aluminum salt- now be removed. Of course, it will be understood by 
8iik'iPi hAde  electiolyie 12 is coated onto the aluminum 25 those skilled in the art that the selection of the load 1 8  
toll 'ir '1 ihin label This layer is preferably less than one will be affected by other considerations such as  the size 
n~liirrneler thick. The cathode 11 comprises a sulfur of the container 16 and the amount of cathode material 
sdlilrdted gr apnlti: cloth placed against the electrolyte 11, as well as the size of the anode 10 and the electrode IT. 
12 SuilaHe mctal electrodes 14 and 15 of carbon or It will be understood that those skilled in the art may 
rr,eial are d t a ~ h e d  to the cathode 11 and the anode 18, 30 make changes and modifications to the foregoing heat 
iespedivcly. The  ell shown in FIG. 3 advantageously activated cell without departing from the spirit and scope 
n:dy b; elihel Soidccl or lolled and placed in a hermetically of the invention as set forth in the claims appended 
\c'i!,il c o n t ~ ~ n e r  such as a foil pouch. hereto. 
A ccil constructed as shown in FIG. 3 and having an What is claimed is: 
AICY-NICI ciecllolyie will deliver about 10 milliamperes 35 1. An EMF cell operated by heat from a heat source 
per square centimeter (rna./cm." of electrolyte area and compnslng: 
?men opclciled at a temperature slightly below 150" C.,  a solid aluminum anode; 
the rnelring pornt of the electrolyte. The cell delivers a cathode comprising a t  least one solid oxidizing ma- 
a b d i  25 ir~s / ~ m . h h e n  it operates at about 200' C. terial which wlll react with the aluminum anode to 
She EMF In b c h  cases is approximately 1.2 volts. 40 form an alummum salt; 
FIG. 4 shows still another form of cell embodying the solid electrolyte disposed between said anode and said 
snvestion. Pnrts corresponding to those in FIGS. 1, 2, cathode and in contact with each, said electrolyte 
and 3 are identrfied by like numerals. The cell of FIG. 4 consisting essentially of at Peast one aluminum salt; 
rocludes an anode 10 in the form of an aluminum rod and 
~vhich extends i ~ t o  a container 16 through a cover plate lmeans for supporting said cathode muterid in a de- 
113 madc of an  electrically insulating material. T'he 45 sired configuration. 
cathode 11 is a molten mixture comprising sodium sul- 2. The cell set forth in claim 1 wherein said means for 
fde, sulfur, and water. An electrode 17 of electrically supporting said cathode material is a porous electrical 
conductive n;,iterial extends through the cover plate 13  conducting material. 
i?:o the anode 11. The electrode 17 may be carbon or a 3. The cell set forth in claim P wherein said cathode 
mctd w h c h  wiQ! not ieact with any of the other materials 50 is a halogen compound. 
~n tile cell. 4. The cell set forth in claim I wherein said heat source 
A current path such as a load in the form of a resistor maintains the cell at a temperature of from about 50" 
18 rimy be connected between the anode 18 and the elec- C.  to about 100" C. 
irode I? to produce a heating effect in the cell. This heat- 5. The cell set forth in claim 1 wherein said electro- 
ing helps sustain operation of the cell. A thin electrolyte 55 lyte is less than about one-eighth inch thick. 
12 oI aluminum sulfide is formed on the aluminum anode 6. The cell set forth in clailm 1 wherein said means for 
1U The electrolyte also serves as a separator by prevent- supporting said cathode is a container; said cathode is a 
lug the cathode 18 material from contacting the anode mixture comprising sodium sulfide, sulfur, and water; 
10. To allow hydrogen sulfide gas to escape as it ac- and said electrolyte is aluminum sulfide. 
curiiulates around the electrode 17 during operation of 60 7. The cell set forth in claim 6 and including an elec- 
t l ~ c  cell, a vent 19 rs provided in the cover plate 13. trode contacting said cathode and further including a 
The ccll shown 11; FIG. 4 is a primary cell and is not load of predetermined value connected between s a d  an- 
icchasgeabie. Tile cell is put into operation in the fol- ode and said electrode to produce a self-sustaining heat- 
Sowing mailr,er. Commercial quality sodium sulfide is ing effect. 
placed in thc contarner 16. Heat is then applied to the 65 8. An E,MF cell operated by heat from a heat source 
continer 116 causing the sodium sulfide to melt into its and comprising: 
own water of hydration. This takes place when the sodium a solid aluminum anode; 
s~.&de is heated to 50" @. or above. When the sodium a cathode comprising at least one solid oxidizing ma- 
qrrlfide is mo1ten. it comprises sodium sulfide, sulfur, and terial which will react with the aluminum anode to 
water. The aluminum anode PO and the carbon electrode 70 form an aluminum salt; 
1"9are then inserted into the molten sodium sulfide, sul- solid electrolyte disposed between said anode and said 
fur, and uaicr mixiure which form the cathode 11. A cathode and in contact with each, said electrolyte 
g.1 oicctivc cant in^ oz aluminum sulfide immediately fox 19s con-ists esscnzialiy of a eutectic mixture of at Beast 
on the aliiminum anode 10. This coating serves as both a one aluminum halide salt and at least one allcali 
ii:para"ir and an electrolyte. 75 halide salt; and 
3,573,986 
5 
means for supporting said cathode material in a de- 2,954,417 
sired configuration. 3,117,032 
9. The cell of claim 8 wherein: 3,121,028 
said anode comprises a sheet of alerminum foil; 3,192,071 
said electr~lyte is a layer coated on to one side of said 3,248,265 
anode and at least one alkali halide salt; and 3,342,715 
said cathode comprises a graphite cloth saturated with 3,423,242 
sulfur and placed agaixst said electrolyte. 3,463,670 
10. The cell set forth in cPaiim 8 wherein said electro- 
lyte is a eutectic mixture of AlCl and NaCI. 
11. The cell set forth in claim 8 wherein said electro- I 0  683,162 
lyte layer is less than about one millimeter thick. 
6 
Lehovec et a!. ---_---- 136-13 
Panzer --_----_ 1 3 6-100 
Story 116-6 
Vinal 136-121 
Herbert ------ -_-  ----- 236-4 
Zarornb 4 36-83 
Meyers et al. -----__-_- ?3G-6 
Rao el al. -_--------- 136-83 
FOREIGN PATENTS 
3/1944 Canada -----------_- 136-83 
References Cited 
UNITED STATES PATENTS 
ALLEIN B. CURTIS, Primary Examiner 
A. SKAPARS, Assistant Examiner 
15 
2,638,489 5/1953 Ruben -_------------ 136-53 U.S. C1. X.R. 
2,718,539 9/1955 Bradshaw et al. ------- 136-83 136-90, 100, 153 
2,759,986 8/1956 Morehouse et al. ---- 136-100 


Heat activated cell Patent

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