A solvent-anchored non-flammable electrolyte

•A non-flammable electrolyte with ionic conductivity of 1.6 mS/cm at 25°C •Ready to use with commercially available separator and electrolyte •Ambient cycling at C/3 and C/10 with no obvious capacity decay •A wide operation range of 25°C–100°C Li-based batteries are ubiquitous in modern-day energy supply systems. However, the volatile and flammable nature of the electrolytes remains a safety challenge. Here, we report that anchored solvent molecules can increase the ionic conductivity of the electrolyte without undermining its non-flammability. Specifically, we developed a liquid-state polymer electrolyte composed of LiFSI salts, dimethoxyethane (DME) solvents, and polysiloxane tethered with ion-solvating moieties. DME coordinates with both the salt and the polymer, while, together with the salt, they synergistically plasticize the polymer to increase the ionic conductivity. The resulting non-flammable polymer electrolyte has a room-temperature ionic conductivity of 1.6 mS/cm and a wide operation window of 25°C–100°C. Benefiting from its liquid nature, our electrolyte can pair with commercially available electrodes without further cell engineering. Our work extends the ionic conductivity range of polymer electrolytes and shows a promising design pathway for next-generation safe and manufacturable electrolytes. Li-based batteries are ubiquitous in modern-day energy supply systems. However, the volatile and flammable nature of the electrolytes remains a safety challenge. Here, we report that anchored solvent molecules can increase the ionic conductivity of the electrolyte without undermining its non-flammability. Specifically, we developed a liquid-state polymer electrolyte composed of LiFSI salts, dimethoxyethane (DME) solvents, and polysiloxane tethered with ion-solvating moieties. DME coordinates with both the salt and the polymer, while, together with the salt, they synergistically plasticize the polymer to increase the ionic conductivity. The resulting non-flammable polymer electrolyte has a room-temperature ionic conductivity of 1.6 mS/cm and a wide operation window of 25°C–100°C. Benefiting from its liquid nature, our electrolyte can pair with commercially available electrodes without further cell engineering. Our work extends the ionic conductivity range of polymer electrolytes and shows a promising design pathway for next-generation safe and manufacturable electrolytes.