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Selenium Edge as a Selective Anchoring Site for Lithium–Sulfur Batteries with MoSe₂/Graphene-Based Cathodes

Wong, Hoilun, Ou, Xuewu, Zhuang, Minghao, Liu, Zhenjing, Hossain, Md Delowar, Cai, Yuting, Liu, Hongwei, Lee, Hwanbin, Wang, Cai-Zhuang, Luo, Zhengtang
ACS applied materials & interfaces 2019 v.11 no.22 pp. 19986-19993
X-ray photoelectron spectroscopy, adsorption, binding sites, cathodes, density functional theory, durability, graphene, graphene oxide, selenides, selenium, sulfur, transmission electron microscopy, vapors
For lithium–sulfur batteries (LSBs), the dissolution of lithium polysulfide and the consequent “shuttle effect” remain major obstacles for their practical applications. In this study, we designed a new cathode material comprising MoSe₂/graphene to selectively adsorb polysulfides on the selenium edges and thus to mitigate their dissolution. More specifically, few-layered MoSe₂ was first grown on nitrogen-doped reduced graphene oxide (N-rGO) using the chemical vapor deposition method and then infiltrated with sulfur as the cathode for LSBs. An initial capacity of 1028 mA h g–¹ was achieved for S/MoSe₂/N-rGO at 0.2 C, higher than 981 and 405.1 mA h g–¹ for pure graphene and sulfur, respectively, along with enhanced cycling durability and rate capability. Moreover, the density functional theory simulation, in addition to the experimental adsorption test, X-ray photoelectron spectroscopy analysis, and transmission electron microscopy technique, reveals the dual roles that MoSe₂ plays in improving the performance of LSBs by functioning as the binding sites for lithium polysulfides and as the platform that enables fast Li-ion diffusion by reducing its diffusion barrier. The reported finding suggests that the transition-metal selenides could be an efficient alternative material as the cathode for LSBs.