Modification of nickel sulfide by surface coating with TiO₂ and ZrO₂ for improvement of cycle capability

TiO₂ - and ZrO₂ -coated nickel sulfide (NiS) were prepared for the improvement of cycle capability in rechargeable lithium batteries with liquid electrolytes. The cells with the TiO₂ -coated NiS showed improved cycle performance as compared with those of the noncoated NiS. This improvement was attributable to the improved structural reversibility of the active materials with Li+ insertion/extraction reactions, which might be due to the stabilization of the active materials by TiO₂, and also attributable to the suppression of sulfur dissolution in the liquid electrolytes. ZrO₂ coating on the NiS surface was not effective for improving the cyclability of the cells, which was attributable to the increase in the amount of metallic Ni clusters, not contributing to the electrochemical redox reactions, when charging.