N-Doped graphene embellished with Co9S8 enable advanced sulfur cathode for high-performance lithium-sulfur batteries

Lithium-sulfur batteries have drawn widespread attention as favorable energy storage systems. However, the low conductivity of S gives rise to a poor specific capacity. Moreover, the shuttle effect of soluble lithium polysulfides (LiPS) causes a rapid performance deterioration in Li-S systems. Herein, Co9S8 implanted on N-doped graphene (Co9S8-NG) is proposed to support S in cathodes. The N-doped graphene substantially enhanced the electronic conductivity of the S-based cathode. Meanwhile, Co9S8 with a high polarity not only effectively immobilized the LiPS species through chemical binding but also considerably catalyzed the LiPS electrochemical conversion, ultimately suppressing its shuttle effect. As expect, the cathode with the Co9S8-NG composite demonstrated high specific capacities of 1051.5 and 564.6 mA h g(-1) at 0.2 and 2 C, respectively. Moreover, a satisfactory cycling stability was displayed at 1 C for 400 cycles, with an average capacity fading of 0.085% per cycle. Therefore, Co9S8-NG was exhibited to improve the cathode performance in numerous aspects and can be regarded as a potential host material to improve the overall performance of Li-S batteries.