Improved high-temperature performance of LiNi0.5Co0.2Mn0.3O2/artificial graphite lithium ion pouch cells by difluoroethylene carbonate

A key issue in the development of lithium ion batteries (LIBs) is the stability of the electrolyte, especially at high temperature. This research compares three electrolyte solvents with different cyclic carbonate structures, i.e. ethylene carbonate (EC), fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC) to investigate their effect on the performance of LiNi0.5Co0.2Mn0.3O2/artificial graphite lithium ion pouch cells at high temperature. The results point out that DFEC is the most effective solvent in preventing interfacial impedance growth and electrolyte decomposition, and improving cycling performance, with capacity retention of 85 % after cycling 500 times at 45 °C. Comprehensive characterizations reveal that DFEC forms effective interphases with high thermal stability on both cathode and anode. This work highlights the important role of DFEC in electrolyte formulations for high−energy−density LIBs at elevated temperature.