Deep eutectic electrolytes for fast charging and wide temperature lithium
metal batteries

Lithium metal batteries offer high energy density. However, it requires electrolytes that remain stable under fastcharging
and wide temperature fluctuation. Here, we develop a sulfonyl-based deep eutectic electrolyte (DEE)
that is nonflammable, thermally stable, and highly conductive (4.1 mS cm􀀀 1 at 30 ◦C). The tailored solvation
structure of this DEE reduced Li+–anion binding and lowered desolvation barriers, as confirmed by spectroscopy,
molecular dynamics, and density functional theory. The DEE formed a robust LiF/SOx-rich solid electrolyte
interphase that enabled long-term cycling. The Li/LFP cells delivered 92 % capacity retention after 1200 cycles at
2C and 30 ◦C. Moreover, Li/LMFP cells retained 75 % after 500 cycles at 2C and 30 ◦C. The electrolyte maintained
stability under fast charging and repeated thermal transitions between 4 and 70 ◦C, highlighting its
adaptability to demanding operating conditions. These findings establish sulfonyle-bas