Anion-derived solid electrolyte interphase realized in usual-concentration electrolyte for Li metal batteries

Constructing anion-derived solid electrolyte interphase (SEI) by recruiting anions into the solvation sheath of Li⁺ is extremely conducive to restrain the dendrite growth of Li metal anode. However, the presence of anions in the solvation sheath of Li⁺ is severely hindered by the solvents with strong coordinating ability in conventional electrolyte. Herein, we boost the content of anions in the primary solvation sheath of Li⁺ by employing a solvent with low donor number, 2-methyltetrahydrofuran, inducing an anion-derived SEI. As a result, the Li||Cu cells show a high average Coulombic efficiency (> 99%) over 500 cycles and the Li||LiFePO₄ cells under a low negative/positive capacity ratio of 2:1 exhibit an impressive capacity retention of 90% after 100 cycles. This work provides insights on constructing stable anion-derived SEI and offers guidance in designing electrolytes for stable Li metal batteries.