Boosting lithium-ion battery performance: the role of a novel carbonate-based ionic liquid electrolyte additive

Abstract

Electrolyte engineering is essential for advancing lithium-ion batteries (LIBs). Here, we introduce a carbonate-based inner-salt ionic liquid additive, ethylene carbonate-activated 1-methylimidazole (MI-EC), that markedly enhances rate capability and cycling stability. Molecular dynamics and electrochemical analyses show that MI-EC strongly coordinates with Li⁺, increasing the lithium-ion transference number. Density functional theory (DFT) calculations reveal its favorable electronic structure (LUMO: −0.82 eV; HOMO: −5.91 eV), which enables preferential interfacial reactions, stable SEI/CEI formation, and suppression of solvent decomposition. With only 1 wt% MI-EC (ME-10), the LFP‖Li half-cell achieves 95.8% capacity retention after 500 cycles at 0.5C (27% higher than that in baseline electrolyte, BE), a 100 mV charge/discharge voltage gap, and 18.8% higher capacity than in BE at 10C. Complementary graphite‖Li and LFP‖graphite cells also deliver superior capacity and rate performance. These findings establish carbonate-based inner-salt ionic liquid additives as a promising route toward durable, high-performance LIB electrolytes.