Molybdenum carbide nanocrystals modified carbon nanofibers as electrocatalyst for enhancing polysulfides redox reactions in lithium‐sulfur batteries. (21st June 2020)

• Record Type: Journal Article
• Authors: Li, Yangyang; Yao, Shanshan; Zhang, Cuijuan; He, Yanping; Wang, Youqiang; Liang, Yazhou; Shen, Xiangqian; Li, Tianbao; Qin, Shibiao; Wen, Wei
• Is Part Of: International journal of energy research. Volume 44:Number 11(2020)
• Page Start: 8388
• Page End: 8398
• Publication Date: 2020-06-21
• Subjects: electrocatalyst -- free‐standing -- lithium‐sulfur batteries -- Mo2C/CFs membrane -- self‐discharge -- shuttle effect; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.5510
• Languages: English
• ISSNs: 0363-907X

Abstract

Summary: The high performance of lithium sulfur (LiS) batteries is the focus of research in recent years. However, the low sulfur loading, shuttling effect in electrolyte, and poor cycling stability limit their applications. Herein, molybdenum carbide nanocrystals embedded carbon nanofibers (Mo2 C@CFs: MCCFs) hybrid membrane was prepared in situ on CFs membrane based on carbonthermal reduction of ammonium molybdate. The fibrous MCCFs network is used as the current collector with Li2 S6 catholyte solution for LiS batteries, which inhibits the shuttle effect and accelerates kinetics redox reaction. In addition, Mo2 C, as electrocatalyst, promotes nucleation of Li2 S of the MCCFs substance, which can reduce polarization and increase the specific capacity. As a result, the free‐standing MCCFs@Li2 S6 electrode (sulfur loading: 4.74 mg) shows a capacity of 977 mAh g −1 and maintains at 828 mAh g −1 at 0.2 C over 250 cycles, and indicates excellent reversibility and cycling stability. Even with sulfur loading as high as 7.11 mg, the MCCF@Li2 S6 electrode exhibits an extremely high capacity of 5.75 mAh. Meanwhile, the Mo2 C modified CFs can be effectively retarding the self‐discharge behavior by trapping the polysulfides. Furthermore, the stability improvement of lithium anode state by effectively suppressing the shuttle effect of polysulfide, played an important role in enhancing the electrochemical performance. Abstract : The freestanding MCCFs inhibited the dissolution of polysulfides shuttle effect and demonstrated as positive electrocatalyst for accelerating kinetic redox reaction of lithium polysulfides/sulfide. In addition, it ialso protects lithium anode and thus efficiently prevented further lithium metal corrosion and electrolyte depletion.