Diluent modified weakly solvating electrolyte for fast-charging high-voltage lithium metal batteries

Weakly solvating electrolyte（WSE） demonstrates superior compatibility with lithium（Li） metal batteries（LMBs）. However, its application in fast-charging high-voltage LMBs is challenging. Here, we propose a diluent modified WSE for fast-charging high-voltage LMBs, which is formed by adding diluent of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether（TTE） into the tetrahydropyran（THP） based WSE. A relatively loose solvation structure is formed due to the formation of weak hydrogen bond between TTE and THP, which accelerates the de-solvation kinetics of Li+. Besides, more anions are involved in solvation structure in the presence of TTE, yielding inorganic-rich interphases with improved stability. Li（30 μm）||Li Ni0.5Co0.2Mn0.3O2（4.1 mAh/cm2） batteries with the TTE modified WSE retain over 64% capacity retention after 175 cycles under high rate of 3 C and high-voltage of 4.5 V, much better than that with pure THP based WSE. This work points out that the combination of diluent with weakly solvating solvent is a promising approach to develop high performance electrolytes for fast-charging high-voltage LMBs.