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

Abstract 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 SnF 2 ‐catalyzed lithiophilic‐lithiophobic gradient solid electrolyte interphase (SCG‐SEI) of Li x Sn y /LiF‐Li 2 O is in situ formed. The superior ionic LiF‐Li 2 O rich upper layer (17.1 nm) possesses high interfacial energy and fast Li + diffusion channels, wherein lithiophilic Li x Sn 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 SnF 2 ‐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, LiFePO 4 ‐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 0.8 Mn 0.1 Co 0.1 O 2 and pouch cell with LiFePO 4 , 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.