Tuning a Weakly-Coordinating Environment via Non-Polar Solvents to Promote Li+ Interfacial Transport in Quasi-Solid-State Li Metal Batteries

Polymer electrolytes offer improved safety and interfacial compatibility for lithium metal batteries (LMBs), yet how Li + solvation chemistry governs interfacial stability, especially under high-voltage operation with high-nickel cathodes, remains poorly understood. Here, we introduce a non-polar solvent regulation strategy by incorporating 3,5-dibromobenzotrifluoride (DBTFB) into an in situ polymer electrolyte to construct a weakly coordinating environment. Combined experimental and theoretical investigations reveal that DBTFB restructures the Li + solvation sheath, lowers the Li + de-solvation energy barrier, and accelerates interfacial ion transport. Meanwhile, its electron-deficient fluorinated aromatic framework promotes robust cathode interphase formation through strong interfacial affinity and anion–π interactions, effectively suppressing lattice oxygen release and transition-metal dissolution on Ni-rich cathodes. Consequently, the resulting electrolyte enables stable cycling of Li||NMC811 cells even at 5 C and delivers excellent cycling stability in 1.5 Ah Gr||NMC622 pouch cells. This work offers a practical pathway toward polymer electrolytes compatible with high-nickel cathodes, facilitating the realization of safe and high-energy-density LMBs for next-generation energy storage.