In Situ Species Analysis of a Lithium-Ion Battery Electrolyte Containing LiTFSI and Propylene Carbonate

In this study, we analyzed the species in a model electrolyte consisting of a lithium salt, lithium bis­(trifluoromethane sulfone)­imide (LiTFSI), and a widely used neutral solvent propylene carbonate (PC) with excess infrared (IR) spectroscopy, ab initio molecular dynamics simulations (AIMD), and quantum chemical calculations. Complexing species including the charged ones [Li+(PC)4, TFSI–, TFSI–(PC), TFSI–(PC)2, and Li­(TFSI)2 –] are identified in the electrolyte. Quantum chemical calculations show strong Li+···O­(PC) interaction, which suggests that Li+ would transport in the mode of solvation-carriage. However, the interaction energy of each hydrogen bond in TFSI–(PC) is very weak, suggesting that TFSI– would transport in hopping mode. In addition, the concentration dependences of the relative population of the species were also derived, providing a scenario for the dissolving process of the salt in PC. These in-depth studies provide physical insights into the structural and interactive properties of the electrolyte of lithium-ion batteries.