Revealing the Dynamic Evolution of Electrolyte Configuration on the Cathode-Electrolyte Interface by Visualizing (De) Solvation Processes

Abstract

Electrolyte engineering is crucial for improving cathode electrolyte interphase (CEI) to enhance the performance of lithium-ion batteries, especially at high charging cut-off voltages. However, typical electrolyte modification strategies always focus on the solvation structure in the bulk region, but consistently neglect the dynamic evolution of electrolyte solvation configuration at the cathode-electrolyte interface, which directly influences the CEI construction. Herein, we reveal an anti-synergy effect between Li⁺-solvation and interfacial electric field by visualizing the dynamic evolution of electrolyte solvation configuration at the cathode-electrolyte interface, which determines the concentration of interfacial solvated-Li⁺. The Li⁺ solvation in the charging process facilitates the construction of a concentrated (Li⁺-solvent/anion-rich) interface and anion-derived CEI, while the repulsive force derived from interfacial electric field induces the formation of a diluted (solvent-rich) interface and solvent-derived CEI. Modifying the electrochemical protocols and electrolyte formulation, we regulate the “inflection voltage” arising from the anti-synergy effect and prolong the lifetime of the concentrated interface, which further improves the functionality of CEI architecture.