Bifunctional Catalytic Effect of CoSe2 for Lithium-Sulfur Batteries: Single Doping versus Dual Doping

Designing catalysts to accelerate the conversion of soluble lithium polysulfides (LiPSs) is regarded as a promising strategy to inhibit the shuttle effect, improving cathode performance of lithium-sulfur batteries (LSBs). Herein, a bifunctional Ni/Zn dual-doped CoSe2 is designed to enhance the catalytic effect of CoSe2. Specifically, Ni functions better in catalyzing the conversion of LiPSs into Li2S with shorter Co-S bond and longer S-S bonds than Zn, while Zn demonstrates a better catalytic effect for Li2S decomposition with reduced Li2S decomposition barrier and elongated Li-S bonds than Ni. Those endows Ni/Zn dual-doped CoSe2 with bifunction in catalyzing conversion reaction of LiPSs and Li2S precipitation as well as the decomposition of Li2S, originating from the modified molecular structure of LiPSs and Li2S. As a result, the sulfur cathode with Ni0.1Zn0.1Co0.8Se2 achieves a rate capability of 681.74 mAh g(-1) at 2C, and a cycling stability for 400 cycles with a decay rate of 0.065%. This work provides an effective way to improve catalytic effect of transition metal compounds for advanced LSBs by homogenous dual doping.