Enabling Stable Operation of Lithium‐Ion Batteries under Fast‐Operating Conditions by Tuning the Electrolyte Chemistry

Abstract

AbstractInferior fast‐charging and low‐temperature performances remain a hurdle for lithium‐ion batteries. Overcoming this hurdle is extremely challenging primarily due to the low conductivity of commercial ethylene carbonate (EC)‐based electrolytes and the formation of undesirable solid electrolyte interphases with poor Li+‐ion diffusion kinetics. Here, a series of EC‐free fast‐charging electrolytes (FCEs) by incorporating a fluorinated ester, methyl trifluoroacetate (MTFA), as a special cosolvent into a practically viable LiPF6–dimethyl carbonate–fluoroethylene carbonate system, is reported. With a solvent‐dominated solvation structure, MTFA facilitates the formation of thin, yet robust, interphases on both the cathode and anode. Commercial 1 Ah graphite|LiNi0.8Mn0.1Co0.1O2 pouch cells filled with the FCE exhibit ≈80% capacity retention over 3000 cycles at 3 C and 4 C (15 min) charging rates in the full range of 0–100% state‐of‐charge. Moreover, even at a low operating temperature of −20 °C, the 1 Ah cell retains a high capacity of 0.65 Ah at a 2 C discharge rate and displays virtually no capacity fade on cycling at a C/5 rate. The work highlights the power of electrolyte design in achieving extra‐fast‐charging and low‐temperature performances.