Regulating Dynamic Solid Electrolyte Interfacial Evolution via α‐H Methyl Substitution Carboxylate Ester Electrolytes Toward 20 Ah Wide‐Temperature (−60°C∼70°C) Li‐Ion Pouch Cells

Abstract

ABSTRACT 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 LiCoO 2 /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.