Lithium-Nickel Sulfide Batteries.
Final rept. 1 Apr 71-31 Mar 72,
TYCO LABS INC WALTHAM MASS
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Investigation of the high rate discharge performance of Ni3S2 indicated that rate capability was strongly influenced by the viscosity of the cell electrolyte. Stable discharges at up to 6 mA sq. cm. equivalent to the 5-hr rate for an electrode of typical thickness were obtained from Teflon-bonded electrodes in a tetrahydrofuranLiClO4 electrolyte. Coulombic efficiencies on the order of 50 of theoretical could be obtained at 3 mA sq. cm. Previous results with propylene carbonate and butyrolactone solutions indicated rate limitations in the vicinity of 0.5 to 1 mA sq. cm. Study of the Ni3S1 oxidation procedure indicated that the optimum temperature for the production of the high voltage material was 325C. X-ray diffraction analysis of the oxidized Ni3S2 indicated the presence of the relatively sulfur rich nickel sulfides Ni7S6 and NiS1.09. These materials possess higher theoretical energy densities than Ni3S2. This advantage is compromised by the difficulty of obtaining high coulombic efficiencies from insulating materials. Oxidation of Ni3S2 at temperatures above 400 C results in the formation of NiO. A brief study of the discharge properties of metallic oxides, carbonates, and cyanides in propylene carbonateLiClO4 electrolyte indicated that although several of these materials exhibited acceptable discharge and voltage efficiencies, none were of sufficient interest to justify further development. Author-PL
- Electrochemical Energy Storage