Ester-Guided Dynamic Li⁺ Solvation Enables Plating-Less, Fast-Charging Li-Ion Batteries.

Abstract

The extremely fast charging (XFC) of Li-ion cells is an urgent milestone in promoting the widespread adoption of electric vehicles. However, EV-targeted cell designs with thicker electrodes compromise the XFC capability when conventional electrolytes are used, leading to hazardous Li plating and a considerable loss in Li inventory. This study presents noncarbonate solvents for superionic conductive, low-viscosity high-concentration electrolytes (HCEs). A methyl acetate (MA)-based HCE with a solid-electrolyte interphase (SEI)-stabilizing additive (3MF) was comparatively examined using a dimethyl carbonate (DMC) solvent, which has an extra oxygen atom in the molecule, across all aspects, including solvation structures, interfacial kinetics, and bulk Li⁺ transport. The 3MF electrolyte demonstrated outstanding XFC performance in a pouch cell (1.2 Ah) format and outperformed DMC-based HCE, showcasing improved cycling performance at low temperatures (-20 °C), 10 C-rate (6-min charging), and with a thick electrode (6.0 mAh cm^-2). By satisfying the energy barrier thresholds for Li⁺ desolvation and Li⁺ migration across the SEI, MA can guide smaller solvation clusters and serve as a molecular lubricant along the Li⁺ percolation pathway in the HCE framework, which is crucial for boosting XFC capabilities.