Solvent-bridged electrolytes for high-energy Li-ion batteries under extreme conditions.

High-capacity anodes are desirable for high-energy lithium-ion batteries but suffer from limited cycle life due to large volume changes during cycling. The LiF-based solid-electrolyte interphase (SEI) has led to prolonged cycling stability. However, current LiF-forming electrolyte designs require anions to enter the Li+ solvation sheath, which inherently reduces the electrolyte's ionic conductivity, limiting both fast-charging and low-temperature performance. Here we develop solvent-bridged electrolytes composed of LiPF6 dissolved in a cosolvent system comprising a bridging cyclic ether that solvates both PF6- and Li+ to form a LiF-rich SEI, and a structural linear ether that governs the electrolyte liquid range. By mitigating direct Li+-anion interactions, the electrolytes maintain high ionic conductivity, enabling stable cycling of micrometre-sized silicon anodes under extreme conditions involving high rates (>4 C), low temperatures (down to -55 °C) and Li plating. Solvent-bridged electrolytes address the intrinsic trade-offs between LiF-rich SEI formation and electrolyte ionic conductivity, offering a promising approach for high-capacity anodes operating under demanding conditions.