Approaching fast ion transport via anion-dipole interaction in weakly solvated electrolytes enables stable Li-plating chemistry.

Abstract

The graphite/Li-metal hybrid anode demonstrates great potential in cycling stability and energy density with designed weakly solvated electrolytes when considering the common issue of solvent co-intercalation and vulnerable interface chemistry with a graphite anode and Li anode, respectively. The weakly solvated electrolytes show weak ion-dipole interaction and promote rapid desolvation but are faced with sluggish ion-transport kinetics, thus inducing high overpotential and Li-dendrite formation. Herein, by applying methyl propionate as a weakly coordinated cosolvent, a loose solvation shell that is regulated by anion-solvent interaction enables weakened Li⁺-anion interaction while maintaining adequate anion participation, featuring a facilitated bulk ion-transport route via anion dissociation, originally achieving a high ionic conductivity of 17.74 mS cm^-1 in weakly solvated electrolytes at 25°C. Consequently, this advanced electrolyte design markedly mitigates concentration polarization and regulates uniform Li deposition, and thus the hybrid anode achieves 99.8% average coulombic efficiency within 1500 cycles at 4C and improved cycling stability at a low N/P ratio of 0.5, making a breakthrough in alkali-metal-ion batteries.