Tuning Solvation Structure Via Inductive and Steric Hindrance Effects for High-Voltage LiCoO2 Batteries.

Abstract

High-voltage lithium cobalt oxide (LiCoO2) has a high specific capacity and energy density, making it a promising cathode material for next-generation lithium-ion batteries (LIBs). However, stabilizing LiCoO2 at elevated charging cut-off voltages remains challenging due to the severe interfacial degradation, particularly the instability of the cathode-electrolyte interphase (CEI) under oxidative conditions. Herein, we propose a novel push-pull electrolyte design strategy by incorporating a non-coordinating diluent, 1H,1H,5H-perfluoropentyl-1,1,2,2-tetrafluoroethylether (HFE), which modulates the Li+ solvation structure through strong inductive and steric hindrance effects, thereby enabling the formation of a robust CEI on the LiCoO2 surface. Guided by molecular electrostatic potential analysis and nuclear magnetic resonance characterizations, the optimized electrolyte creates a tailored solvation environment that suppresses parasitic interfacial reactions and facilitates the formation of a bilayer interphase. As a result, the LiCoO2 cathode exhibits excellent electrochemical stability with the HFE-containing electrolyte, delivering over 300 stable cycles at 4.6 V in high-loading LiCoO2//Li cells (∼11 mg cm-2) and retaining 77% capacity after 200 cycles in LiCoO2//Graphite full-cells at 4.5 V. This solvation engineering strategy provides a promising pathway toward next-generation high-voltage LiCoO2-based batteries.