Anion competition for Li+ solvated coordination environments in poly(1,3 dioxolane) electrolyte to enable high-voltage lithium metal solid-state batteries

Gel-based polymer electrolytes are limited by the polarity of the residual solvent, which restricts the coupling-breaking behaviour during Li+ conduction, resulting in the Li+ transport kinetics being greatly affected. Here, we designed anion competitive gel polymer electrolyte (ACPE) by introducing lithium difluoro (oxalato)borate (LiDFOB) anion into the 1,3-dioxolane (DOL) in situ polymerisation system. ACPE enhances the ionic dipole interaction between Li+ and the solvent molecules and synergizes with Li+ across the solvation site of the polymer ethylene oxide (EO) unit, combination that greatly improves the Li+ transport efficiency. As a result, ACPE exhibits 1.12 mS cm−1 ionic conductivity and 0.75 Li+ transfer number at room temperature. Additionally, this intra-polymer solvation sheath allows preferential desolvation of DFOB−, which contributes to the formation of kinetically stable anion-derived interphase and effectively mitigates side reactions. Our results demonstrate that the assembled Li||NCM622 solid-state battery exhibits lifespan of over 300 cycles with average Coulombic efficiency of 98.8% and capacity retention of 80.3%. This study introduces a novel approach for ion migration and interface design, paving the way for high-safety and high-energy-density batteries.