Anion-Derived Solid Electrolyte Interphase Enabled by Diluent Modulated Dimethyl Carbonate-Based Localized High Concentration Electrolytes for Lithium Metal Batteries

Carbonate-based electrolytes generally suffer from low Coulombic efficiency and poor cycling stability in lithium metal batteries. In this work, localized high concentration electrolytes (LHCEs) based on dimethyl carbonate (DMC) with varying diluent additions are designed. LHCEs demonstrate higher Li+ transference numbers and a greater proportion of contact ion pairs (CIPs) and ion pair aggregates (AGGs) in the solvation structures, facilitating the formation of anion-derived solid electrolyte interphase (SEI). Furthermore, LHCEs enhance the Coulombic efficiency of Li||Cu cells and improve the anodic stability against lithium. One of these LHCEs, prepared with appropriate diluent addition, exhibits excellent capacity retention in Li||NCM622 cells at 0.5 C after 150 cycles, thus presenting promising possibilities for the development of high energy density lithium metal batteries. Localized high concentration electrolytes (LHCEs) have a unique AGG-dominant solvation structure that can facilitate the formation of an anion-derived SEI. The diluent addition ratios affect the components of the SEI. LHCE-2 : 1, with the appropriate diluent ratio, improves the Coulombic efficiency and the cycling stability in lithium metal batteries. Furthermore, it exhibits excellent capacity retention in Li||NCM622 cells at 0.5 C. image