A Biocompatible Deep Eutectic Electrolyte Enables Ultra‐Fast Charging in Lithium‐Ion Batteries

Abstract Lithium‐ion batteries are of great significance in improving people's lives by offering reliable, long‐lasting, and high‐capacity power solutions. However, safety concerns, particularly those related to electrolyte leakage under harsh conditions, pose significant obstacles to their practical applications. In this context, a biocompatible deep eutectic electrolyte (DEE) is presented formulated by blending 2,6‐dimethylpyrazine (DMPY)—a natural ingredient approved by the World Health Organization (WHO) due to its natural origin—with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in specific molar ratios. Benefitting from its abundant N atoms, DMPY molecule effectively drives Li─N coordination with Li + cations, forms hydrogen bonds with TFSI − anions, and consequently enhances the dissociation of LiTFSI—all of which trigger the formation of DEE. This DEE solution demonstrates remarkable performance characteristics, including a high Li + transference number (0.67), substantial ion conductivity (0.57 mS cm −1 at 30 °C), and moderate oxidation voltage (4.10 V vs Li/Li + ). These attributes are complemented by remarkable interface stability and long‐term cycling stability across a broad range of rates, notably at a rate of 10 C, ascribed to the generation of a robust organic–inorganic gradient solid‐electrolyte interphase. This work opens intriguing perspectives to design novel electrolytes for the demanded performance of lithium‐ion batteries while ensuring good biocompatibility.