Charge–discharge mechanism of mechanically alloyed NiS used as a cathode in rechargeable lithium batteries

Nickel sulfide (NiS) as a cathode material for a lithium rechargeable battery was charged and discharged at elevated temperature (80 °C) using a PEO solid polymer electrolyte. In order to synthesize a homogeneous NiS phase, very fine nickel metal powder was ball milled with sulfur powder for 12 h under argon gas. We found using ex-situ XRD measurements that the NiS cathode active material was transformed into other phases such as Ni3S2, nickel and sulfur during discharge. The initial discharge capacity of the NiS positive electrode was 580 mAh/g NiS at 1.5 V vs. Li/Li+ with PEO electrolyte. It has good cycling properties, retaining 93% of the initial discharge capacity even after 200 cycles with a PEO solid polymer electrolyte.