Fluorine-Rich Interphase and Desolvation Regulation for a Long-Life and High-Rate TiS₂-Based Li-Metal Battery
2022
Cao, Tianqi | Huang, Shizhi | Sun, Yonggang | Wang, Shijie | Wu, Yuelong | Ma, Hui | Chai, Yuqiao | Chen, Ruoqi | Zhang, Huanrong | Chen, Dong | Wang, Xusheng | Chen, Jitao | Xue, Mianqi
Structural stability and electrochemical stability make titanium disulfide (TiS₂) a promising cathode material for Li-metal battery. Building the good compatibility of electrolyte with TiS₂ and Li metal is key to improving the performance of TiS₂-based Li-metal battery, and related tricky issues are the unstable solid electrolyte interphase (SEI) and slow Li⁺ transportation kinetics. Here we design an electrolyte of lithium bis(fluorosulfonyl)imide (LiFSI) in methyl 2,2,2-trifluoroethyl carbonate (FEMC) for a TiS₂-based Li-metal battery. On the one hand, the reduction of LiFSI and FEMC generates robust fluorine-rich SEIs on both the surfaces of TiS₂ and Li metal, thereby elevating the cycling stability. On the other hand, the weak solvation ability of FEMC enables fast charge transfer, thus improving the rate capability. The Li⁺ transportation kinetics processes of Li⁺ conduction in bulk electrolyte, Li⁺ desolvation, Li⁺ migration across SEI, and Li⁺ diffusion in bulk TiS₂ are studied with different electrolytes. The results reveal that the Li⁺ transportation kinetics in the TiS₂-based Li-metal cell is mainly controlled by Li⁺ desolvation. This electrolyte regulation for interphase stability and Li⁺ kinetics is also applicable to other battery systems.
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