SUPERELASTIC ELECTRODE FOR SECONDARY BATTERY USING TI-NI ALLOYS

초록

Sulfide electrode was fabricated on the surface of a Ti-50Ni(at%) alloy by annealing the alloy at various sulfur pressures, and then microstructures, shape memory effect and superelasticity of the electrode were investigated. Morphology of surface sulfide changed from granular shape to porous shape with increasing sulfur pressure from 40 kPa to 80 kPa, which was related with the change from NiS(2) to NiS. Two-layered sulfide was observed in which the inner layer was mainly Ti(8.2)S(11) and the outer layer was a mixture of NiS(2) and NiS. A Ti-50Ni alloy with the surface sulfide layers showed the shape memory effect and superelasticity clearly. Multi voltage plateaus of 2.00 V, 1.89 V, 1.70 V and 1.42 V were observed at a cell with the sulfide electrode. NiS(2) was not transformed into pure Ni and Li(2)S directly during discharging process but it was transformed into them by way of intermediate phases such as NiS and Ni(3)S(2).

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