SnF2‐Catalyzed Lithiophilic–Lithiophobic Gradient Interface for High‐Rate PEO‐Based All‐Solid‐State Batteries

Polyethylene oxide (PEO)-based all-solid-state lithium metal batteries (ASSLMBs) are strongly hindered by the fast dendrite growth at the Li metal/electrolyte interface, especially under large rates. The above issue stems from the suboptimal interfacial chemistry and poor Li⁺ transport kinetics during cycling. Herein, a SnF₂-catalyzed lithiophilic-lithiophobic gradient solid electrolyte interphase (SCG-SEI) of Li_xSn_y/LiF-Li₂O is in situ formed. The superior ionic LiF-Li₂O rich upper layer (17.1 nm) possesses high interfacial energy and fast Li⁺ diffusion channels, wherein lithiophilic Li_xSn_y alloy layer (8.4 nm) could highly reduce the nucleation overpotential with lower diffusion barrier and promote rapid electron transportation for reversible Li⁺ plating/stripping. Simultaneously, the insoluble SnF₂-coordinated PEO promotes the rapid Li⁺ ion transport in the bulk phase. As a result, an over 46.7 and 3.5 times improvements for lifespan and critical current density of symmetrical cells are achieved, respectively. Furthermore, LiFePO₄-based ASSLMBs deliver a recorded cycling performance at 5 C (over 1000 cycles with a capacity retention of 80.0 %). More importantly, impressive electrochemical performances and safety tests with LiNi_0.8Mn_0.1Co_0.1O₂ and pouch cell with LiFePO₄, even under extreme conditions (i.e., 100 °C), are also demonstrated, reconfirmed the importance of lithiophilic-lithiophobic gradient interfacial chemistry in the design of high-rate ASSLMBs for safety applications.