Improved interfacial compatibility between flame-retardant electrolytes and graphite electrodes by tuning the solvation structure of Li+

Abstract

Conventional electrolytes with flammability and volatility may incur severe safety issues, which are impeding the application of lithium batteries on a large scale. Flame-retardant solvents are introduced into the electrolytes to enhance the security performance, while the battery electrochemical performance is compromised due to incompatibility between these solvents and graphite (Gr) anode. In this work, a flame-retardant electrolyte prepared by trimethyl phosphate (TMPa), lithium difluoro(oxalato)borate (LiDFOB) and fluoroethylene carbonate (FEC) could be expected to solve the dilemma via regulating the solvation structure of Li+ to suppress the co-intercalation effect of TMPa with Li+ and alleviate the compatibility issues of interface caused by the continuous reduction of LiDFOB. The formation mechanism of the solid electrolyte interface (SEI) at the graphite electrode was analyzed to explore the intrinsic reaction of the electrolyte at the electrode interface. The 300-cycle capacity retention of Li|Gr cell at 0.5C reaches 97.48 %, and the deposition and stripping performance of the Li|Li symmetric cell is also significantly improved. Such Li+ solvation structure modification provides a new idea for fire-extinguishing electrolyte design and helps to promote the industrialization of safe and eco-friendly electrolytes.