Ni sulfides were formed on a Ni-deposited Ti-50.0Ni( at) alloy by annealing under a sulfur pressure of 100 kPa at 673K for 0.36 ks. Martensitic transformation, superelasticity and electrochemical properties were characterized using different techniques. Ni sulfides consisting of NiS and NiS2 of thickness 0.8 mu m were formed by a reaction between Ni and S. Some spherical particles and pores were found in the sulfides. A Ti-50.0Ni alloy with Ni sulfide surface layers showed a two-stage B2-R-B19 ' transformation behavior. A partial superelasticity with a superelastic recovery ratio of 78% found in a current collector showed a clear discharge behavior with a voltage plateau between 1.3-1.6V. Discharge capacities of the Ni sulfide cathode decreased largely from 700 to 510 mAh(g-NiS2)(-1) with increasing number of cycles up to 3, above which it decreased gradually.