Preparation of NiS2 using spark-plasma-sintering process and its electrochemical properties

Single-phase NiS2, which was hardly prepared by conventional processes such as mechanical milling or precipitation reaction, was prepared using the spark plasma sintering (SPS) process. Using porous Ni (porosity 95%) as a starting material, similar-shaped porous NiS2 (porosity 89%), containing trace amounts (ca. 3%) of NiS, and finally single-phase NiS2 powder were obtained by the SPS process. The electrochemical tests demonstrated that the present NiS2 samples showed the initial discharge capacity of ca. 820 mAh g(-1), which was similar to 94% of the theoretical value. The capacity retention after 10 cycles was ca. 19%, and such rapid degradation was mainly attributable to the irreversibility of the Li extraction from the lithiated (discharged) NiS2 electrodes and the electrical disconnections among the active materials, carbon powders, and/or current collectors. (C) 2008 The Electrochemical Society.