An Unprecedented Fireproof, Anion‐Immobilized Composite Electrolyte Obtained via Solidifying Carbonate Electrolyte for Safe and High‐Power Solid‐State Lithium‐Ion Batteries

The update of electrolytes from a liquid state to a solid state is considered effective in improving the safety and energy density of lithium-ion batteries (LIBs). Although numerous efforts have been made, solid-state electrolytes' (SSEs) insufficient charge transfer capability remains a significant obstruction to practical applications. Herein, a fireproof and anion-immobilized composite electrolyte is designed by solidifying carbonate electrolyte, exhibiting superior Li-ion conductivity (11.5 mS cm-1 at 30 °C) and Li-ion transference number (0.90), which endows LIBs excellent rate capability and cycling stability. Elaborate characteristics and theoretical calculations demonstrate the presence of robust anion-molecule coordination (composed of lithium bond and Coulomb force) enables a more efficient ion transport, where the mobility of Li+ ion is enhanced meanwhile the anions are immobilized. This work highlights how the strong interactions between electrolyte components can be used to simultaneously regulate the migration of Li+ ion and anion, and realize a one-step conversion of inflammable liquid-state electrolyte to nonflammable solid-state electrolyte.