Miniature Li⁺ solvation by symmetric molecular design for practical and safe Li-metal batteries

Developing high-safety Li-metal batteries (LMBs) with rapid rechargeability represents a crucial avenue for the widespread adoption of electrochemical energy storage devices. Realization of LMBs requires an electrolyte that combines non-flammability with high electrochemical stability. Although current electrolyte technologies have enhanced LMB cyclability, rational electrolyte fabrication capable of simultaneously addressing high-rate performance and safety remains a grand challenge. Here we report an electrolyte design concept to enable practical, safe and fast-cycling LMBs. We created miniature anion–Li⁺ solvation structures by introducing symmetric organic salts into various electrolyte solvents. These structures exhibit a high ionic conductivity, low desolvation barrier and interface stabilization. Our electrolyte design enables stable, fast cycling of practical LMBs with high stability (LiNi_0.8Co_0.1Mn_0.1O₂ cell (twice-excessed Li): 400 cycles) and high power density (pouch cell: 639.5 W kg⁻¹). Furthermore, the Li-metal pouch cell survived nail penetration, revealing its high safety. Our electrolyte design offers a viable approach for safe, fast-cycling LMBs.