Ultrafine Co 3 Se 4 Nanoparticles in Nitrogen‐Doped 3D Carbon Matrix for High‐Stable and Long‐Cycle‐Life Lithium Sulfur Batteries

Lithium–sulfur batteries are a promising high energy output solution for substitution of traditional lithium ion batteries. In recent times research in this field has stepped into the exploration of practical applications. However, their applications are impeded by cycling stability and short life‐span mainly due to the notorious polysulfide shuttle effect. In this work, a multifunctional sulfur host fabricated by grafting highly conductive Co 3 Se 4 nanoparticles onto the surface of an N‐doped 3D carbon matrix to inhibit the polysulfide shuttle and improve the sulfur utilization is proposed. By regulating the carbon matrix and the Co 3 Se 4 distribution, N‐CN‐750@Co 3 Se 4 ‐0.1 m with abundant polar sites is experimentally and theoretically shown to be a good LiPSs absorbent and a sulfur conversion accelerator. The S/N‐CN‐750@Co 3 Se 4 ‐0.1 m cathode shows excellent sulfur utilization, rate performance, and cyclic durability. A prolonged cycling test of the as‐fabricated S/N‐CN‐750@Co 3 Se 4 ‐0.1 m cathode is carried out at 0.2 C for more than 5 months which delivers a high initial capacity of 1150.3 mAh g −1 and retains 531.0 mAh g −1 after 800 cycles with an ultralow capacity reduction of 0.067% per cycle, maintaining Coulombic efficiency of more than 99.3%. The reaction details are characterized and analyzed by ex situ measurements. This work highly emphasizes the potential capabilities of transition‐metal selenides in lithium–sulfur batteries.