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

Abstract The graphite/Li-metal hybrid anode demonstrates great potential in cycling stability and energy density with designed weakly-solvated electrolytes, considering the common issue of solvent co-intercalation and vulnerable interface chemistry with graphite anode and Li anode, respectively. The weakly-solvated electrolytes show weak ion-dipole interaction and promote rapid desolvation but face 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 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 endowing 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.