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.