High sulfur loading and shuttle inhibition of advanced sulfur cathode enabled by graphene network skin and N, P, F-doped mesoporous carbon interfaces for ultra-stable lithium sulfur battery
Haotian Liu, Fan Liu, Zehua Qu, Jieling Chen, Hui Liu, Yiqing Tan, Jiabao Guo, Yan Yan, Shuang Zhao, Xinsheng Zhao, Xinming Nie, Xin Ma, Zengxia Pei, Mingkai Liu
Abstract
Achieving high loading of active sulfur yet rational regulating the shuttle effect of lithium polysulfide (LiPS) is of great significance in pursuit of high-performance lithium-sulfur (Li-S) battery. Herein, we develop a free-standing graphene-nitrogen (N), phosphorus (P) and fluorine (F) co-doped mesoporous carbon-sulfur (G-NPFMC-S) film, which was used as a binder-free cathode in Li-S battery. The developed mesoporous carbon (MC) achieved a high specific surface area of 921 m<sup>2</sup>·g<sup>–1</sup> with a uniform pore size distribution of 15 nm. The inserted graphene network inside G-NPFMC-S cathode can effectively improve its electrical conductivity and simultaneously restrict the shuttle of LiPS. A high sulfur loading of 86% was achieved due to the excellent porous structures of graphene-NPFMC (G-NPFMC) composite. When implemented as a freestanding cathode in Li-S battery, this G-NPFMC-S achieved a high specific capacity (1,356 mAh·g<sup>–1</sup>), favorable rate capability, and long-term cycling stability up to 500 cycles with a minimum capacity fading rate of 0.025% per cycle, outperforming the corresponding performances of NPFMC-sulfur (NPFMC-S) and MC-sulfur (MC-S). These promising results can be ascribed to the featured structures that formed inside G-NPFMC-S film, as that highly porous NPFMC can provide sufficient storage space for the loading of sulfur, while, the N, P, F-doped carbonic interface and the inserted graphene network help hinder the shuttle of LiPS via chemical adsorption and physical barrier effect. This proposed unique structure can provide a bright prospect in that high mass loading of active sulfur and restriction the shuttle of LiPS can be simultaneously achieved for Li-S battery.