Diphenylguanidine combined with high molecular weight polyacrylonitrile precursor for high-conductivity and high-sulfur-loading cathode of lithium-sulfur battery

Abstract

Sulfurized polyacrylonitrile (SPAN) cathode have high discharge specific capacity, close to 100 % coulombic efficiency and excellent cycle stability, which is regarded as a very promising cathode material in lithium-sulfur batteries. However, polyacrylonitrile as vulcanization precursor have a great influence on the performance of SPAN. Therefore, the effects of different molecular weight polyacrylonitrile precursors while diphenylguanidine as vulcanization accelerator on the performance of SPAN cathodes are reported for the first time. Considering that diphenylguanidine as vulcanization accelerator can significantly increase the sulfur loading of SPAN. Prepared SPAN-1000k cathode by an ultra-high molecular weight polyacrylonitrile precursor (Mw = 1000k) has a sulfur-loading of up to 54.5 %. Surprisingly, a 22 % increase in conductivity resulting in a remarkable discharge capacity of 830 mAh gcomposite−1 at a high rate of 1C (0.7 A/g). This work demonstrates that diphenylguanidine as vulcanization accelerator prepared ultra-high molecular weight SPAN cathode can greatly improve sulfur loading and conductivity, and exhibit excellent electrochemical performance at a high rate.