Regulating Dynamic Solid Electrolyte Interfacial Evolution via α-H Methyl Substitution Carboxylate Ester Electrolytes...

High reactivity of the α-H sites in carboxylates is the root cause of inert interfacial evolution, where the resultant solvent co-intercalation and α-H-mediated oxide hydrogenation contribute to non-recover capacity loss and limited calendar cycle life, especially for wide-temperature-range applications. Herein, to regulate dynamic interfacial evolution, we ingeniously designed an ethyl isobutyrate (EI) based electrolyte via α-H methyl substitution for practical LiCoO₂/graphite (LCO||Gr) pouch cells. By replacing the strongly electron-withdrawing α-H group with an inert methyl group, the inherent solvent nucleophilicity is preserved, while the ESP_min is significantly enhanced. Such specific solvation structure evolution can facilitate the involvement of EI in inner solvation sheath and further induce a dense, stable interface which can suppress the hydrogenation-initiated capacity loss of delithiated LCO cathodes. Employing electrochemical DRT and ToF-SIMS techniques, we demonstrate that EI can interrupt the solvent co-intercalation process at Gr anode by stabilizing interfacial dynamics and suppress anodic self-discharge. Consequently, the 2 Ah LCO||EI||Gr pouch cell retains approximately 96.4% capacity after 700 cycles at -20°C and exhibits overseeding 250 cycles at 45°C. Furthermore, the commercial 20 Ah LCO||EI||Gr pouch cells deliver high energy densities of 160.3 Wh kg^-1 at -60°C and 229.1 Wh kg^-1 at 70°C, which exhibit superior temperature resistance.