Fluorinating solid electrolyte interphase by regulating polymer–solvent interaction in lithium metal batteries

The cycling stability of high-energy-density lithium (Li) metal batteries is severely hindered by uneven Li deposition, which is caused by the heterogeneous transport of Li ions in solid electrolyte interphase (SEI) on the surface of Li metal anodes. LiF-rich SEI emerges as a promising solution to improve homogeneous transport of Li ions. Herein, constructing LiF-rich SEI by regulating the interaction between the polymer coating on Li metal anode and fluoroethylene carbonate (FEC) in electrolytes was demonstrated. The polymer coating with uniformly distributed polar functional groups can interact with intermediate decomposition products of FEC, promoting the formation of LiF. LiF-rich SEI ensures improved uniformity of Li deposition, which promises stable operation of Li metal batteries under practical conditions for 143 cycles in comparison with 89 cycles of control group. Moreover, a prototype pouch cell of 1.0 Ah maintains a capacity retention of 90% after 180 cycles. This work provides a fresh attempt to construct LiF-rich SEI by regulating the interaction between solvent and polymer for long-cycling Li metal batteries.