Electron-Donating or -Withdrawing Groups of Carbonate Solvent on Lithium-Ion (De)intercalation Chemistry

Cyclic carbonate solvents have been extensively utilized as cosolvents and/or additives in formulating electrolytes for lithium-ion batteries. However, their application often relies on empirical knowledge, lacking a universally applicable perspective to elucidate how different functional groups in cyclic carbonates affect battery performance. Herein, by focusing on the substituted functional group at the α-H in the ethylene carbonate (EC) solvent, it is discovered that solvents containing electron-withdrawing groups (e.g., −F) enable reversible Li⁺ (de)intercalation in graphite electrodes, while those with electron-donating groups (e.g., −CH₃, −CH₂CH₃) may lead to Li⁺-solvent cointercalation. Furthermore, solvents with electron-withdrawing groups can help the electron-donating groups achieve Li⁺ (de)intercalation, whereas the reverse is not feasible. These phenomena are elucidated through intermolecular interactions, characterized by 2D ¹H-¹⁹F heteronuclear Overhauser enhancement spectroscopy, revealing interactions between electron-withdrawing and -donating groups in the electrolyte solvation structure. This study offers insights into the roles of electron-donating or -withdrawing groups in electrolyte formulations.