Steric Hindrance Manipulation in Polymer Electrolytes toward Wide-Temperature Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (LMBs) based on polymer electrolytes have become a hot topic for next-generation energy storage owing to their high specific energy, flexibility, and simple preparation process. However, poor electrolyte–electrode interface reactions and intrinsically slow Li⁺ transfer kinetics limit the development of solid-state LMBs. Here, a tris(4-fluorophenyl)phosphine (T4FPP) additive with strong steric hindrance and weak coordination is introduced to remodel the Li⁺ coordination environment to facilitate electrolyte bulk and interface charge transfer. Furthermore, theoretical analysis combined with in situ/ex situ characterizations demonstrate that the addition of T4FPP helps to construct an anion-dominated solvation structure through molecular crowding and form a LiF/Li₂O-rich SEI layer. Ultimately, the LFP|Li full cell based on the T4FPP modified electrolyte works normally even at 10 C with a reversible specific capacity of 88.9 mAh g^–1. Simultaneously, the electrochemical performance at 0–60 °C further verified the wide temperature range adaptability of the electrolyte.