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AssigneeThe United States of America as represented by the Secretary of the Army
InventorsCharles W. Walker, Jr., William L. Wade, Jr., Michael Binder, Sol Gilman
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A cathode is provided for use in high energy primary lithium-thionyl chloe cell systems or calcium-thionyl chloride cell systems. The cathode comprises an expanded metallic current collector screen into which has been pasted a mixture of a low surface area conductive carbon black and a high surface area conductive carbon black previously mixed with a binder.
A cathode for use in a high energy primary thionyl chloride cell system said cathode comprising an expanded metallic current collector screen bearing a dried pasted mixture of a low surface area conductive carbon black and a high surface area conductive carbon black previously mixed with a binder wherein the low surface area conductive carbon black has a surface area of about 60 m.sup.2 /gm and the high surface area conductive carbon black has a surface area of about 1475 m.sup.2 /gm, wherein the low surface area conductive carbon black is mixed with the high surface area conductive carbon black in the ratio of about 75 parts by weight low surface area black to about 25 parts by weight of high surface area black, wherein the binder is a polytetrafluoroethylene emulsion and wherein the mixture of carbon blacks is mixed with polytetrafluoroethylene emulsion in the ratio of about 100 parts by weight of carbon black mixture to about 10 parts by weight of polytetrafluoroethylene emulsion.
A high energy primary cell system comprising lithium as the anode, a solution of an inorganic lithium salt in thionyl chloride as the electrolyte, and an expanded metallic current collector screen bearing a dried pasted mixture of a low surface area conductive carbon black and a high surface area conductive carbon black previously mixed with a binder as the cathode wherein the low surface area conductive carbon black has a surface area of about 60 m.sup.2 /gm and the high surface area conductive carbon black has a surface area of about 1475 m.sup.2 /gm, wherein the low surface area conductive carbon black is mixed with the high surface area conductive carbon black in the ratio of about 75 parts by weight low surface area conductive carbon black to about 25 parts by weight high surface area conductive carbon black, wherein the binder is a polytetrafluoroethylene emulsion, and wherein the mixture of carbon blacks is mixed with polytetrafluoroethylene in the ratio of about 100 parts by weight of carbon black mixture to about 10 parts by weight of polytetrafluoroethylene emulsion.
A high energy primary cell system comprising calcium as the anode, a solution of an inorganic calcium salt in thionyl chloride as the electrolyte, and an expanded metallic current collector screen bearing a dried pasted mixture of a low surface area conductive carbon black and a high surface area conductive carbon black previously mixed with a binder as the cathode wherein the low surface area conductive carbon black has a surface area of about 60 m.sup.2 /gm and the high surface area conductive carbon black has a surface of about 1475 m.sup.2 /gm, wherein the low surface area conductive carbon black is mixed with the high surface area conductive carbon black in the ratio of about 75 parts by weight low surface area conductive carbon black to about 25 parts by weight high surface area conductive carbon black, wherein the binder is a polytetrafluoroethylene emulsion, and wherein the mixture of carbon blacks is mixed with polytetrafluoroethylene emulsion in the ratio of about 100 parts by weight of carbon black mixture to about 10 parts by weight of polytetrafluoroethylene emulsion.
Dependencies are inferred from the claim text.
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This invention relates to a cathode suitable for use in high energy primary thionyl chloride cell systems and to high energy primary thionyl chloride cell systems including the cathode.
In the field of high energy primary cells, the thionyl chloride cell system appears very attractive for its high open circuit potentials, high theoretical energy density, broad operating temperature ranges and storeability. Both calcium and lithium cells have been studied. The main incentive for using calcium in place of the more popular lithium is that calcium anodes have higher melting temperatures than lithium anodes. The disparity between the melting points of these two metals is of special interest since 839.degree. C. required to melt calcium would not likely be reached by any internally driven cell condition. This precludes the likelihood of difficulties traceable to a molten anode leading to thermal run aways often seen in lithium-thionyl chloride cells.
However, carbon cathode capacities tend to be lower for calcium based cells than for analogous lithium cells due to formation of a glassy calcium chloride deposit rather than the crystalline lithium chloride deposit normally formed in lithium based cells.
The drawing shows discharge curves obtained by galvanostatic discharge measured at 20 mA/cm.sup.2 for:
(a) a cathode made from (SAB) in a cell with a Ca anode and an electrolyte of 1 molar Ca(AlCl.sub.4).sub.2 in thionyl chloride
(b) a cathode made from 75(SAB)/25(BP) with a Ca anode and an electrolyte of 1 molar Ca(AlCl.sub.4).sub.2 in thionyl chloride
The improvement in cell performance obtained by using the blend of carbon blacks in the cathode in both the lithium-thionyl chloride and calcium-thionyl chloride systems is clearly seen from the drawing.
In lieu of (SAB) as the low surface area conductive carbon black, one can use any other carbon black having a surface area less than 100 m.sup.2 /gm.
The high surface area conductive carbon blacks that can be used are those having a surface area above 250 m.sup.2 /gm.