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

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.