Thermal battery cells containing cathode materials in low-melting nitrate electrolytes

Abstract

The addition of cathode materials comprising Cu ++ , Fe +++ , Cr +++ or Au +++ , in the form of salts such as the nitrate or halide, e.g. Fe(NO 3 ) 3 or CuCl 2 , to low melting nitrate electrolyte cells increases cell potential. Other ions such as Co ++ , Eu +++ , La +++ , Ni ++ , Mn ++ , Ce +++ , Pr +++ , Nd +++ , Gd +++ , Sm +++ and Tb +++ , in the form of salts thereof, can also be used, but yield smaller cell potentials. Such cathodic materials in the form of a suitable salt, such as a nitrate or halide, e.g. Fe(NO 3 ) 3 or CuCl 2 , are added to low melting fused nitrate electrolytes, e.g. a LiNO 3 , KNO 3 mixture, in a concentration sufficient to increase cell potential, using Li or Ca anodes. A suitable metal current collector such as a Ni screen can be used as a cathode. The above cathodic materials can be used in conjunction with other cathodic materials such as AgNO 3 , which undergoes reduction to the free metal.

What is claimed is: 
     
       1. A thermal electrochemical cell comprising a low melting nitrate electrolyte which is a non-conductive solid at ambient temperature and is capable of becoming an ionically conductive liquid upon being heated above its melting point,   a cathode material in said electrolyte, said cathode material comprising a metal ion selected from the group consisting of Cu ++ , Fe +++ , Cr +++ , Au +++ , Co  ++ , Eu ++ , La +++ , Ni ++ , Mn ++ , Ce +++ , Pr +++ , Nd +++ , Gd +++ , Sm +++   and Tb +++   ions and mixtures thereof, and   an anode in contact with said electrolyte, and selected from the group consisting of Li and Ca anodes.   
     
     
       2. The thermal cell of claim 1, said nitrate electrolyte having a melting point and being capable of activation at temperatures not greater than about 200° C. 
     
     
       3. The thermal cell of claim 1, said nitrate electrolyte being selected from the group consisting of mixtures of (1) LiNO 3  and KNO 3 , (2) LiNO 3  and NaNO 3 , (3) LiNO 3 , NaNO 3  and KNO 3  and (4) LiNO 3  and RbNO 3 . 
     
     
       4. The thermal cell of claim 3, said nitrate electrolyte being a LiNO 3 , KNO 3  mixture. 
     
     
       5. The thermal cell of claim 1, said nitrate electrolyte including a nitrite. 
     
     
       6. The thermal cell of claim 1, wherein said cathode material is a salt containing said metal ion. 
     
     
       7. The thermal cell of claim 2, wherein said cathode material comprises a metal ion selected from the group consisting of Cu ++ , Fe +++ , Cr +++   and Au +++ . 
     
     
       8. The thermal cell of claim 6, wherein said cathode material is selected from the group consisting of nitrate and halide salts of said metal ion. 
     
     
       9. The thermal cell of claim 6, wherein the concentration of said cathode material in said electrolyte ranges from about 2×10 -  to about 2×10 -  molal. 
     
     
       10. The thermal cell of claim 7, wherein said cathode material is a soluble salt of said metal ion selected from the group consisting of nitrate and chloride salts. 
     
     
       11. The thermal cell of claim 6, wherein said electrolyte is LiNO 3  /KNO 3 , and wherein the concentration of said cathode material is said electrolyte ranges from about 2×10 -4   to about 2×10 -1  molal. 
     
     
       12. The thermal cell of claim 6, and including a cathode current collector in contact with said electrolyte and spaced from said anode. 
     
     
       13. The thermal cell of claim 6, said metal salt cathode material comprising a solid layer in said electrolyte spaced from said anode. 
     
     
       14. The thermal cell of claim 9, said cathode material also including a silver salt in a proportion of about 0.01 to about 1 mole per mole of said salt containing said metal ion. 
     
     
       15. The thermal cell of claim 10, wherein said electrolyte is LiNO 3  /KNO 3 , and wherein the concentration of said cathode material in said electrolyte ranges from about 2×10 -4  to about 2×10 -1  molal. 
     
     
       16. In a thermal electrochemical cell comprising an anode, a cathode and an electrolyte disposed between said anode and said cathode, a low melting nitrate electrolyte which is a non-conductive solid at ambient temperature and is capable of becoming an ionically conductive liquid upon being heated above its melting point, said nitrate electrolyte having a melting point and being capable of activation at temperatures not greater than about 200° C.,   a cathode material diffused in said electrolyte, said cathode material comprising a metal ion selected from the group consisting of Cu ++ , Fe +++ , Cr +++ , Au +++ , Co ++ , Eu +++ , La +++ , Ni ++ , Mn ++ , Ce +++ , Pr +++ , Nd +++ , Gd +++ , Sm +++   and Tb +++ , and mixtures thereof, and   an anode in contact with said electrolyte, and selected from the group consisting of Li and Ca anodes.   
     
     
       17. The thermal cell of claim 16, and including a cathode current collector in contact with said electrolyte and spaced from said anode. 
     
     
       18. The thermal cell of claim 17, said nitrate electrolyte being selected from the group consisting of mixtures of (1) LiNO 3  and KNO 3 , (2) LiNO 3  and NANO 3 , (3) LiNO 3 , NaNO 3  and KNO 3  and (4) LiNO 3  and RbNO 3  ; and said cathode material is a salt containing said metal ion. 
     
     
       19. The thermal cell of claim 17, said nitrate electrolyte being a LiNO 3 , KNO 3  mixture, and wherein said cathode material is a soluble salt of said metal ion selected from the group consisting of nitrate and chloride salts. 
     
     
       20. The thermal cell of claim 19, wherein the concentration of said cathode material in said electrolyte ranges from about 2×10 -4  to about 2×10 -1  molal.