Carbonized Polyacrylonitrile‐Stabilized SeSx Cathodes for Long Cycle Life and High Power Density Lithium Ion Batteries

A facile synthesis of selenium sulfide (SeS_x)/carbonized polyacrylonitrile (CPAN) composites is achieved by annealing the mixture of SeS₂ and polyacrylonitrile (PAN) at 600 °C under vacuum. The SeS_x molecules are confined by N‐containing carbon (ring) structures in the carbonized PAN to mitigate the dissolution of polysulfide and polyselenide intermediates in carbonate‐based electrolyte. In addition, formation of solid electrolyte interphase (SEI) on the surface of SeS_x/CPAN electrode in the first cycle further prevents polysulfide and polyselenide intermediates from dissolution. The synergic restriction of SeS_x by both CPAN matrix and SEI layer allows SeS_x/CPAN composites to be charged and discharged in a low‐cost carbonate‐based electrolyte (LiPF₆ in EC/DEC) with long cycling stability and high rate capability. At a current density of 600 mA g^?1, it maintains a reversible capacity of 780 mAh g^?1 for 1200 cycles. Moreover, it retains 50% of the capacity at 60 mA g^?1 even when the current density increases to 6 A g^?1. The superior electrochemical performance of SeS_x/CPAN composite demonstrates that it is a promising cathode material for long cycle life and high power density lithium ion batteries. This is the first report on long cycling stability and high rate capability of selenium sulfide‐based cathode material.