Design Unsaturated Selenium Coordinated NbSe2‐x as Multifunctional Sulfur Electrocatalyst toward Fast and Durable Sulfur Reduction Reaction

Abstract Lithium‐sulfur (Li‐S) battery are considered as the next generation energy storage system owing to their ultra‐high theoretical specific capacity and energy density. However, the commercialization of Li‐S battery is still hindered by the intrinsically low conductivity of sulfur, sluggish catalytic conversion and notorious shuttle effect of polysulfides. The implantation of defects in sulfur electrocatalyst can effectively increase its conductivity and catalytic efficiency of lithium polysulfides, but the current mainstream defective materials are limited and lack of in‐depth research. Herein, a defective niobium selenide (NbSe 2‐x ) nanosheet sulfur electrocatalyst is constructed with enriched selenium defects, which demonstrates strong interaction with sulfur species, endowing NbSe 2‐x with rapid and reliable sulfur reduction reaction. As a result, the Li‐S cell with NbSe 2‐x exhibits excellent multiplicative performance in both coin cell and pouch cell, which maintains stable cycling for over 2000 cycles under 5 C, corresponding to a low‐capacity fading rate of 0.024% per cycle. Ah level pouch cell is also fabricated, showing a decent energy density of 378 Wh kg −1 . This creative strategy not only emphasizes the importance of selenium defect engineering in Li‐S batterie toward practical application, but also enlightens the material engineering to realize superior performance in related energy storage and conversion area.