Cathode material for use in a high temperature rechargeable molten salt cell and high temperature rechargeable molten salt cell including the cathode material

Abstract

Binary sulfides of chromium of the formula Cr 2 S 3 , Cr 3 S.s4, and CrS are used as the cathode in a high temperature molten rechargeable salt cell. The cathode material is thermally stable at high temperatures and also provides high specific energy densities and specific power densities to that the cell can be used in pulse power, electric propulsion and load leveling applications.

What is claimed is: 
     
       1. A cathode material for use in high temperature rechargeable molten salt-cells, said cathode material including binary sulfides of chromium of the formula Cr 2  S 3 , Cr 3  S 4 , and CrS. 
     
     
       2. A high temperature rechargeable molten salt cell including a lithium aluminum alloy of about 48 atomic percent lithium as the anode, a lithium halide eutectic mixture of about 31 mole percent of molten lithium chloride, about 47 mole percent of molten lithium bromide, and about 22 mole percent of molten lithium fluoride with a melting point of about 445° C. as the electropyte, and a mixture of about 25 mole percent of chromium metal and about 75 mole percent of lithium sulfide as the cathode, wherein the cell is in an electrochemically reduced state and is activated to form the Cr 2  S 3 , Cr 3  S 4 , and CrS cathode material by electrically charging the cell to a cell voltage limit of about 1.6 V at a temperature above the melting point of the electrolyte. 
     
     
       3. A high temperature rechargeable molten salt cell including an alkali metal ion containing anode, a molten alkali metal halide electrolyte and binary sulfides of chromium as the cathode. 
     
     
       4. A high temperature rechargeable molten salt cell according to claim 3 wherein the binary sulfides of chromium are Cr 2  S 3 , Cr 3  S 4 , and CrS. 
     
     
       5. A high temperature rechargeable molten salt cell according to claim 3 wherein the chromium sulfide cathode is formed insitu by the electrochemical oxidation of chromium metal and an alkali metal sulfide of the group consisting of Li 2  S, Na 2  S and K 2  S. 
     
     
       6. A high temperature rechargeable molten salt cell according to claim 3 wherein the chromium sulfide cathode is formed insitu by the electrochemical oxidation of a mixture of chromium metal and sulfur. 
     
     
       7. A high temperature rechargeable molten salt cell according to claim 3 wherein the alkali metal containing anode is at least one member taken from the group consisting of lithium, lithium-aluminum alloys, lithium-boron alloys, sodium, solium-lead alloys, potassium, calcium, and magnesium. 
     
     
       8. A high temperature rechargeable molten salt cell according to claim 7 wherein the anode is a lithium aluminum alloy of about 48 atomic percent lithium. 
     
     
       9. A high temperature rechargeable molten salt cell according to claim 3 wherein the molten alkali metal halide electroylte is at least one molten alkali metal halide taken from the group consisting of molten LiAlCl 4 , molten NaAlCl 4 , molten LiCl, molten LiF. molten LiBr, molten NaCl, molten NaF, molten NaBr, molten KCl, molten KF, and molten KBr. 
     
     
       10. A high temperature rechargeable molten salt cell according to claim 9 wherein the molten alkali metal halide electrolyte is a eutectic mixture of about 47 mole percent of molten lithium bromide, about 31 mole percent of molten lithium chloride, and about 22 mole percent of molten lithium fluoride. 
     
     
       11. A high temperature rechargeable molten salt cell according to claim 9 where the molten alkali metal halide electrolyte is a eutectic mixture of about 59 mole percent of molten lithium chloride and about 41 mole percent of molten potassium chloride.