A solvent molecule reconstruction strategy enabling a high-voltage ether-based electrolyte

Abstract

Electrolytes of high compatibility with Li metal anodes (LMAs) and high voltage resistance are critical for high-energy-density Li-metal batteries (LMBs). Localized high-concentration electrolytes (LHCEs) have been recently demonstrated, which, however, require an extremely high salt-to-solvent ratio (SSR; SSR ≥ 1 : 2). Decreasing the SSR without sacrificing the electrochemical performance is a huge challenge. Here, we propose a solvent molecule reconstruction strategy to construct a 1,3-dioxolane (DOL)-based “localized middle-concentration electrolyte” with a low SSR (1 : 3.6), which possesses superior Li compatibility (Coulombic efficiency: ∼99.2%) and high voltage resistance (∼4.7 V). A controllable polymerization process is utilized to scavenge the unstable free DOL solvent molecules and reconstruct them to form polyethers with intrinsically higher oxidation resistance. More importantly, the scavenging and reconstruction of free DOL solvent molecules induce the generation of more favorable anion-rich solvation configurations, which can effectively passivate the anode and cathode with a high content of inorganic fluorides as well as elastic polyether-derived segments. As a result, the assembled Li||NCM622 full cell equipped with our DOL-based “localized middle-concentration electrolyte” can stably cycle at a high cut-off voltage of 4.6 V and achieve a high energy density of 347.1 W h kg⁻¹. This work provides an effective strategy for modulating the solvation structures with less salt usage and can enrich the advanced electrolyte systems for high-energy-density LMBs.