HIGH CAPACITY CATHODE MATERIAL WITH IMPROVED RATE CAPABILITY PERFORMANCE
The present invention related 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, cobalt sulfate and sulfur. The cathode material of the present invention provides an increased rate pulse performance compared to iron disulfide cathode material. 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 which is electrochemically oxidizable to form metal ions in the cell upon discharge to generate an electron flow in an external electrical circuit electrically connected to the cell;
b) a cathode of electrically conductive material, wherein the cathode comprises a metal matrix material comprising a first metal salt comprising iron, a second metal salt comprising cobalt and sulfur; and
c) an ionically conductive electrolyte solution activating the anode and the cathode.
2 . The electrochemical cell of claim 1 wherein the metal matrix material comprises the general formula Fe 1-x Co x S 2 wherein x≧0.5.
3 . The electrochemical cell of claim 1 wherein the metal matrix material comprises the general formula Fe 1-x Co x S 2 wherein 0.5≦x≦1.0.
4 . The electrochemical cell of claim 1 wherein the metal matrix comprises a catalyst comprising a sodium salt.
5 . The electrochemical cell of claim 1 wherein the first metal salt is selected 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.
6 . The electrochemical cell of claim 1 wherein the second metal salt is selected from the group consisting of cobalt sulfate (CoSO 4 ), cobalt acetate Co(C 2 H 3 O 2 ) 2 , cobalt chloride (CoCl 3 ), cobalt chloride (CoCl 2 ), cobalt fluoride (CoF 2 ), cobalt iodate (CoI 2 ), cobalt thiocyanate (Co(SCN) 2 ) and respective hydrate forms thereof.
7 . An electrochemical cell having an anode comprising lithium electrochemically oxidizable to form metal ions in the cell upon discharge to generate an electron flow in an external electrical circuit electrically connected to the cell, a cathode of electronically conductive material, and an ionically conductive electrolyte solution activating the anode and the cathode, the cathode comprising a metal matrix material characterized as a reaction product of iron sulfate, cobalt sulfate and sulfur, wherein the metal matrix material has a stoichiometric formulation consisting of either Fe 0.3 Co 0.7 S 2 or Fe 0.2 Co 0.8 S 2 .
8 . The electrochemical cell of claim 7 wherein the mixture of the iron sulfate and cobalt sulfate includes iron in either the iron(VI), iron(V), iron(IV), iron(III), iron(II), iron(I) or iron(0) oxidation states.
9 . The electrochemical cell of claim 7 wherein the mixture of the iron sulfate and the cobalt sulfate includes cobalt in either the cobalt(V), cobalt(IV), cobalt(III), cobalt(II), cobalt(I) or cobalt(0) oxidation states.
10 . The electrochemical cell of claim 7 wherein the metal matrix comprises a catalyst comprising a sodium salt of sodium thiosulfate pentahydrate (Na 2 S 2 O 3 .5H 2 O).
11 . The electrochemical cell of claim 7 wherein the metal matrix material is prepared from starting materials comprising iron sulfate, cobalt sulfate, and sulfur reacted by one of the group consisting of a thermal treatment, sol-gel formation, chemical vapor deposition and hydrothermal synthesis of the starting materials.
12 . The electrochemical cell of claim 7 wherein the cathode further comprises a binder material.
13 . The electrochemical cell of claim 12 wherein the binder material is a fluoro-resin powder.
14 . The electrochemical cell of claim 7 wherein the cathode further comprises a conductive additive material.
15 . The electrochemical cell of claim 14 wherein the conductive additive material is selected from the group consisting of carbon, graphite and a combination thereof.
16 . The electrochemical cell of claim 7 wherein the electrolyte solution comprises a Group IA metal salt dissolved in a nonaqueous solvent.
17 . The electrochemical cell of claim 16 wherein the nonaqueous solvent comprises an inorganic solvent.
18 . The electrochemical cell of claim 16 wherein the nonaqueous solvent comprises an organic solvent.
19 . A cathode for an electrochemical cell, the cathode comprising a metal matrix material characterized as a reaction product formed by either a hydrothermal decomposition reaction or a hydrothermal addition reaction of an aqueous mixture of a first metal salt comprising iron, a second metal salt comprising cobalt and sulfur, the metal matrix material having a general formula Fe 1-x Co x S 2 wherein x≧0.5.
20 . The cathode of claim 19 wherein the first metal salt comprises iron in either the iron(VI), iron(V), iron(IV), iron(III), iron(II), iron(I) or iron(0) oxidation state.
21 . The cathode of claim 19 wherein the second metal salt comprises cobalt in either the cobalt(V), cobalt(IV), cobalt(III), cobalt(II), cobalt(I) or cobalt(O) oxidation state.
22 . The cathode of claim 19 wherein the metal matrix material is prepared from starting materials comprising iron sulfate, cobalt sulfate and sulfur reacted together by one of the group consisting of a thermal treatment, sol-gel formation, chemical vapor deposition and a hydrothermal synthesis.
23 . The cathode of claim 19 wherein the cathode further comprises a binder material.
24 . The cathode of claim 23 wherein the binder material is a fluoro-resin powder.
25 . The cathode of claim 19 wherein the cathode further comprises a conductive additive material.
26 . The cathode of claim 25 wherein the conductive additive material is selected from the group consisting of carbon, graphite and a combination thereof.
27 . The cathode of claim 19 wherein the first metal salt is selected 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.
28 . The cathode of claim 19 wherein the second metal salt is selected from the group consisting of cobalt sulfate (CoSO 4 ), cobalt acetate Co(C 2 H 3 O 2 ) 2 , cobalt chloride (CoCl 3 ), cobalt chloride (CoCl 2 ), cobalt fluoride (CoF 2 ), cobalt iodate (CoI 2 ), cobalt thiocyanate (Co(SCN) 2 ) and respective hydrate forms thereof.
29 . A method of making a cathode for an electrochemical cell, the cathode comprising a metal matrix material, which method comprises:
a) combining a first metal salt comprising iron, a second metal salt comprising cobalt and sulfate to provide a metal salt matrix admixture;
b) reacting the metal salt matrix admixture to provide the metal matrix material having the general formula Fe 1-x Co x S 2 wherein x≧0.5; and
c) forming the metal oxide matrix material into a cathode.
30 . The method of claim 29 including heating the metal salt matrix admixture to a temperature of from about 100° C. to 300° C.
31 . The method of claim 29 including adding de-ionized water to the metal salt matrix admixture.
32 . The method of claim 29 including selecting the 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.
33 . The method of claim 29 including selecting the second metal salt from the group consisting of cobalt sulfate (CoSO 4 ), cobalt acetate Co(C 2 H 3 O 2 ) 2 , cobalt chloride (CoCl 3 ), cobalt chloride (CoCl 2 ), cobalt fluoride (CoF 2 ), cobalt iodate (CoI 2 ), cobalt thiocyanate (Co(SCN) 2 ) and respective hydrate forms thereof.