Gear Meshing Effect Induced Chemical and Mechanical Dual‐Reinforced Interfaces for Stable Quasi‐Solid‐State Lithium Metal Batteries

Abstract Chemical–mechanical coupling failure between the NCM cathode and polymer electrolytes (PEs), including interfacial side reaction and irreversible contact failure, severely impedes the commercialization of high‐energy‐density quasi‐solid‐state polymer lithium metal batteries (QSPLMBs). Herein, a chemical and mechanical dual‐reinforced interfacial stabilization strategy triggered by the van der Waals interactions between polymer and solvent within PEs is explored. Specifically, the electronegative fluorine (δ − F) in the poly(2,2,2‐trifluoroethyl acrylate) (PTA) and the electropositive hydrogen (δ + H) in the mixed solvent of propylene carbonate and triethyl phosphate induce directional meshing through electrostatic attraction. The interaction weakens the solvent–Li + coordination, increasing the proportion of anions in the solvation structure, while enabling solvents to function as dynamic cross‐linking mediators, facilitating the deformation reversibility of the PTA network, defined as “gear meshing effect.” Cryo‐electron microscopy and in situ techniques demonstrate that the effect results in the formation of an interfacial structure, which is composed of an anion‐derived cathode–electrolyte interface and a robustly adhesive PE, thereby effectively interrupting chemical–mechanical coupling failure. The constructed Li|PE|NCM811 cell exhibits prolonged cycling stability, retaining 76.3% of its capacity after over 1400 cycles, and maintains excellent performance under low‐temperature conditions. This work presents an innovative solution for the long‐term stability of high‐energy‐density QSPLMB interfaces.