Localized Deep Eutectic Electrolytes for Durable 4.8 V Lithium Metal Batteries

Lithium metal batteries employing lithium-rich manganese-based oxide (LRMO) cathode promise ultrahigh energy density (more than 500 Wh kg^-1), offering a disruptive route for power sources of electric vehicles and low-altitude aircraft, etc. Nevertheless, conventional electrolytes with weak anion-solvent interactions fail to form robust interfaces on both high-voltage LRMO cathodes and highly reactive lithium metal anodes. Here, we design a localized deep eutectic electrolyte (LDEE) by introducing a highly fluorinated ether diluent into a deep eutectic electrolyte (DEE). This diluent triggers electronic redistribution within hydrogen bond donors, relocating and intensifying hydrogen-bonding active sites. As a result, while maintaining strong Li⁺ solvation, the anion-solvent interactions are reinforced, and the anionic solvation structure is locally compacted. Both the cathodic interface and the anodic interphase are derived from anions, suppressing parasitic reactions at the lithium anode and mitigating lattice-oxygen release from the LRMO cathode. The battery with LDEE maintains 80% capacity after 200 cycles within 2-4.8 V. Benefiting from this electrolyte, the as-assembled 12.8 Ah LRMO||Li pouch cell delivers a high energy density of 616.2 Wh kg^-1 and exhibits excellent safety under nail penetration and 130 °C oven tests. This work provides a viable strategy for achieving high energy density and long cycling stability in lithium metal batteries.