Polymer‐Ion Interaction Prompted Quasi‐Solid Electrolyte for Room‐Temperature High‐Performance Lithium‐Ion Batteries

Abstract Lithium‐ion batteries using quasi‐solid gel electrolytes (QSEs) have gained increasing interest due to their enhanced safety features. However, their commercial viability is hindered by low ionic conductivity and poor solid–solid contact interfaces. In this study, a QSE synthesized by in situ polymerizing methyl methacrylate (MMA) in 1,2–dimethoxyethane (DME)‐based electrolyte is introduced, which exhibits remarkable performance in high‐loading graphite||LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) pouch cells. Owing to the unique solvent‐lacking solvation structure, the graphite exfoliation caused by the well‐known solvent co‐intercalation is prohibited, and this unprecedented phenomenon is found to be universal for other graphite‐unfriendly solvents. The high ionic conductivity and great interfacial contact provided by DME enable the quasi‐solid graphite||NCM811 pouch cell to demonstrate superior C‐rate capability even at a high cathode mass loading (17.5 mg cm ^‐2 ), surpassing liquid carbonate electrolyte cells. Meanwhile, the optimized QSE based on carbonates exhibits excellent cycle life (92.4% capacity retention after 1700 cycles at 0.5C/0.5C) and reliable safety under harsh conditions. It also outperforms liquid electrolytes in other high‐energy‐density batteries with larger volume change. These findings elucidate the polymer's pivotal role in QSEs, offering new insights for advancing quasi‐solid‐state battery commercialization.