Backbone-Mediated Coordination-Environment Reshaping in Gel Polymer Electrolytes for High-Voltage Lithium Metal Batteries.

Abstract

Conventional linear polyether electrolytes feature abundant ether-oxygen sites that dominate the primary Li+ solvation shell, limiting anion participation and undermining ion transport and high-voltage stability. A backbone-mediated coordination-environment reshaping strategy is proposed by incorporating diglycidyl 1,2-cyclohexanedicarboxylate (DCD) into the copolymerization of 1,3-dioxolane (DOL), yielding an in situ crosslinked gel polymer electrolyte, P(DCD-DOL). The weakly coordinating ester carbonyl groups and the spatially restricted ether-oxygen sites in the crosslinked network jointly weaken backbone-Li+ coordination and promote anion/solvent participation in the Li+ solvation shell. Multiscale characterizations and theoretical simulations confirm that P(DCD-DOL) effectively optimizes the Li+ solvation structure, leading to a high Li+ transference number of 0.64, an oxidative stability window of 5.20 V, and inorganic-rich electrode-electrolyte interphases. Consequently, Li||NCM811 cells with P(DCD-DOL) retain 84.21% capacity after 500 cycles at 4.3 V, and 80.62% after 200 cycles at 4.5 V. Moreover, a 0.9 Ah pouch cell achieves an energy density of 305 Wh kg-1 and retains 82.33% capacity over 180 cycles. This work highlights polymer backbone engineering as an effective route to regulate Li+ coordination and interfacial chemistry in high-voltage lithium metal batteries.