Ferroelectric Dipoles Tailoring Solid-Electrolyte-Interphase Chemistry to Enable Reversible Lithium Metal Batteries

Solid-electrolyte interphase (SEI) plays a decisive role in building reliable Li metal batteries. However, the scarcity of anions in Helmholtz layer (HL) caused by electrostatic repulsion usually leads to the inferior SEI derived from solvents, resulting in dendrites and 'dead' Li. Therefore, regulating the distribution of anions in electric double layer (EDL) and continuously introducing more anions into HL to tailor anions-derived SEI is crucial for achieving stable Li plating/stripping. Herein, by jointly utilizing the controlled defects of reduced graphene oxide (rGO) and the oriented dipoles of ferroelectric BaTiO₃ (BTO), the rGO-BTO composite layer sustainedly brings more TFSI^- and NO₃ ^- into anion-defecient HL, promoting favorable decomposition of anions and guiding the generation of robust and fast-Li⁺-transport SEI containing more inorganics LiF and Li₃N species. Thus, the resulting Li deposit shows smooth and dense morphologies without dendrites, leading to high average Coulombic efficiency. The Li//Cu@rGO-BTO (10 mAh cm^-2 plated Li) cell exhibits an enhanced Li plating/stripping stability (2700 h) and a higher rate capability. The LiFePO₄ full cell (N/P≈6.3) using rGO-BTO displays an enhanced capacity retention (82.0 % @ 430 cycles). This work provides a new insight on the construction of robust SEI by regulating the distribution of anions within EDL.