Rational Design of Vinylene Carbonate-Inspired 1,3-Dimethyl-1H-imidazol-2(3H)-one Additives to Stabilize High-Voltage...

Lithium metal batteries (LMBs) employing high-voltage nickel-rich cathodes represent a promising strategy to enable higher energy density storage systems. However, instability at the electrolyte-electrode interfaces (EEIs) currently impedes the translation of these advanced systems into practical applications. Herein, 1,3-dimethyl-1H-imidazol-2(3H)-one (DMIO), integrating structural features of vinylene carbonate (VC) while substituting oxygen with electron-donating nitrogen, has been synthesized and validated as a multifunctional electrolyte additive for high-voltage LMBs. Theoretical calculations and experimental results demonstrate that the potent electron-donating nitrogen in DMIO enables preferential DMIO oxidation at the cathode while preserving its carbon-carbon double bond for a concomitant reduction on the anode. Thereby, robust DMIO-derived EEIs are generated, reinforcing cycling in the full cells. Additionally, DMIO leverages Lewis acid-based interactions to coordinate and sequester protons from acidic LiPF₆ decomposition byproducts, concurrently retarding LiPF₆ hydrolysis while attenuating parasitic consumption of EEIs by acidic species. Consequently, incorporating DMIO into conventional carbonate electrolytes enables an improved capacity retention of Li||NCM622 cells to 81% versus 26% in the baseline electrolyte after 600 cycles. Similarly, DMIO improves Li anode cycling performance, displaying extended life spans over 200 h in Li||Li symmetric cells and enhancing Coulombic efficiency from 76% to 88% in Li||Cu cells. The synergistic effects of DMIO on both the cathode and anode lead to substantially improved cell lifetime. This rationally designed, multifunctional electrolyte additive paradigm provides vital insights that can be translatable to further electrolyte molecular engineering strategies.