Preparation of Highly-Cyclized Sulfurized Polyacrylonitrile for Lithium-Sulfur Batteries

Sulfurized polyacrylonitrile (SPAN) is regarded as an attractive cathode candidate of lithium-sulfur (Li-S) batteries for its non-dissolution mechanism and effective alleviation of polysulfides shuttling issue in Li-S batteries, displaying high utilization of cathode active material, outstanding cycle stability and structural stability. However, the relation between cyclization degree and cycle stability of SPAN is still unveiled. In this work, SPAN-C-V composites were synthesized by co-introduction of CuSO₄ and zinc n-ethyl-n-phenyldithiocarbamate (ZDB) in the co-heating of sulfur and polyacrylonitrile. The co-introduction of CuSO₄ and ZDB reduced the cyclization reaction onset temperature of PAN while increased the C—C/C=C within SPAN-C-V, thus led to an increase in the degree of cyclization of SPAN-C-V, achieving excellent electrochemical performance by simultaneously improving the cyclization degree and increasing the content of sulfur. The SPAN-C-V exhibited an initial reversible capacity of 805 mAh·g^-1 and 601 mAh·g^-1 after 100 cycles with the capacity retention rate of 93% at 0.2 C (1 C = 600 mAh·g^-1). The focus on the cyclization degree of SPAN provides an enlightenment of advanced cathode material.