Moderate Dissociating Solvation Structure-Mediated Electrolytes for High-Voltage Lithium-Ion Batteries

Lithium-ion batteries (LIBs) face challenges in the stability and electrode compatibility of conventional electrolytes at high voltages and extreme temperatures. Here, we present an electrolyte design featuring a moderately dissociating solvation structure, achieved by combining lithium difluoro(oxalato)borate (LiDFOB) with ethyl propionate (EP). This formulation promotes the formation of abundant contact ion pairs (CIPs), which effectively weaken Li+–solvent interactions, enhance oxidative stability, and lower Li+ desolvation energy. As a result, graphite || LiNi0.8Co0.1Mn0.1O2 (NCM811) full cells deliver outstanding long-term cycling stability at 4.5 V (vs Li/Li+) across a wide temperature range, retaining 94.2% capacity after 300 cycles at −20 °C and 92.5% after 100 cycles at 60 °C. An interfacial model reveals how the optimized solvation structure, governed by moderately dissociating Li+–anion interactions, enhances interfacial stability and cycling performance under demanding conditions. This work underscores the pivotal role of solvation structure engineering in advancing electrolyte stability in next-generation LIBs.