CoS2 as a Sulfur Redox-Active Cathode Material for High-Capacity Nonaqueous Zn Batteries

Nonaqueous Zn-ion batteries are a promising candidate for a high-energy storage system to replace Li-ion batteries. Here, we report on CoS2 as a cathode material for Zn-ion batteries using nonaqueous electrolytes, one exhibiting a maximum capacity of 283 mAh/g. Compositional, valence state, and structural studies reveal Zn2+ de/intercalation mediated by reversible interconversions between 2S(2-) (sulfide) and S-2(2-) (disulfide) forms of sulfur, which is the first such known case operating in a multivalent system. Our findings suggest that anionic redox-active cathode materials offer considerable promise in realizing high capacities in multivalent batteries.