High capacity cathode material with improved operating voltage
View Patent ↗The present invention relates to an electrochemical cell comprising an anode of a Group IA metal and a cathode of a composite material prepared from an aqueous mixture of iron sulfate, nickel sulfate, and sulfur. The cathode material of the present invention provides for a lithium electrochemical cell having an increased operating voltage and power performance with high discharge capacity as compared to a lithium cell comprising nickel disulfide cathode material. In addition, the cathode material of the present invention exhibits a smaller initial irreversible voltage loss as compared to iron disulfide. This makes the cathode material of the present invention particularly useful for implantable medical applications.
1. An electrochemical cell, comprising:
a) an anode of a Group IA metal;
b) a cathode comprising iron nickel disulfide having the general formula Fe x Ni 1-x S 2 , wherein 0.15≦x≦0.25;
c) a separator positioned between the anode and the cathode; and
d) an ionically conductive electrolyte activating the anode and the cathode.
2. The electrochemical cell of claim 1 wherein the cathode comprises a binder material.
3. The electrochemical cell of claim 2 wherein the binder material is a fluoro-resin powder.
4. The electrochemical cell of claim 1 wherein the cathode comprises a conductive additive material.
5. The electrochemical cell of claim 4 wherein the conductive additive material is selected from the group consisting of carbon, graphite, and a combination thereof.
6. An electrochemical cell, comprising:
a) an anode comprising lithium;
b) a cathode comprising a cathode active material of either Fe 0.15 Ni 0.85 S 2 or Fe 0.25 Ni 0.75 S 2 ;
c) a separator positioned between the anode and the cathode; and
d) an ionically conductive electrolyte activating the anode and the cathode.
7. The electrochemical cell of claim 6 wherein the cathode comprises a binder material.
8. The electrochemical cell of claim 7 wherein the binder material is a fluoro-resin powder.
9. The electrochemical cell of claim 6 wherein the cathode comprises a conductive additive material.
10. The electrochemical cell of claim 9 wherein the conductive additive material is selected from the group consisting of carbon, graphite, and a combination thereof.
11. The electrochemical cell of claim 6 wherein the electrolyte comprises a Group IA metal salt dissolved in a nonaqueous solvent.
12. The electrochemical cell of claim 11 wherein the nonaqueous solvent comprises an inorganic or organic solvent.
13. A method for making a cathode active material for an electrochemical cell, the method comprising the steps of:
a) selecting a first metal salt from the group consisting of iron sulfate (FeSO 4 ), iron acetate (Fe(C 2 H 3 O 2 ) 2 ), iron bromide (FeBr 3 ), iron perchlorate (Fe(ClO 4 ) 2 ), iron iodate (FeI 2 ), iron nitrate (Fe(NO 3 ) 3 ), iron oxalate (Fe(C 2 O 4 ) 3 ), iron thiocyanate (Fe(SCN) 3 ), and respective hydrate forms thereof;
b) selecting a second metal salt from the group consisting of nickel sulfate (NiSO 4 ), nickel chloride (NiCl 2 ), nickel formate (Ni(CHO 2 ) 2 ), nickel hypophosphite (Ni(H 2 PO 2 ) 2 ), and respective hydrate forms thereof;
c) mixing the first metal salt and the second metal salt with sulfur to thereby provide a metal salt matrix admixture; and
d) reacting the metal salt matrix admixture to provide the cathode active material having the general formula Fe x Ni 1-x S 2 , wherein 0.15≦x≦0.25.
14. The method of claim 13 including heating the metal salt matrix admixture to a temperature of from about 100° C. to 300° C.
15. The method of claim 13 including adding de-ionized water to the first metal salt and the second metal salt mixed with sulfur prior to reacting the resulting metal salt matrix admixture to provide the cathode active material.