Construction of CoS₂ Reduction Accelerator-Modified Sulfurized Polyacrylonitrile Nanofibers as High-Performance Cathode Materials for Practical Lithium-Sulfur Batteries

Sulfurized polyacrylonitrile (SPAN) is an attractivecathode materialfor lithium-sulfur batteries because of its high theoreticalenergy density, good cyclic stability, and low self-discharging rate.However, the slow reaction kinetics enormously limits the actual capacityand rate performance of SPAN cathodes. In the present work, SPAN nanofiberscontaining a certain amount of CoS2 were used to preparehigh-performance cathode materials for lithium-sulfur batteries,and the redox kinetics of sulfur conversion was promoted by impartingcatalytic activities to SPAN. Specifically, Co was uniformly distributedin CoS2-SPAN nanofibers in the form of CoS2,which reduced the charge transfer impedance in the electrode, acceleratedthe conversion of short-chain polysulfide to Li2S/Li2S2, increased the migration rate of lithium ions,and improved the kinetics of the redox reaction. Hence, after thesulfurization of polyacrylonitrile nanofibers containing 4 wt % ofCoCO(3), CoS2-SFPAN manifested a high reversiblecapacity of 762 mAh g(-1) (composite) at 0.2C, an excellent multiplicative performance of 592 mAh g(-1) (composite) at 4.0 C, and an extremely stable cycle lifeof more than 500 cycles at 1.0 C. When the cathode was tested undera high areal loading (S) of 5.5 mg cm(-2) and a leanelectrolyte (E) condition of E/S = 10 & mu;L mg(-1), it maintained high reversible capacities of 710 mAh g(-1) (composite) at 0.1 C and 652 mAh g(-1) (composite) at 0.2 C.