Study on reaction mechanism of carbonate based electrolytes, lithium salts and cathode materials to improve fire safety in lithium-ion batteries – A review

Lithium-ion batteries (LIBs) are commonly used as an essential source of energy in several applications (i.e. electric vehicles, electronic devices etc.) due to their superior energy storage capabilities and high energy density. Various technologies have been introduced for energy density optimization; however, fire safety is a major challenge that should examine their safety attributes. This review aims to establish an appropriate threshold for the electrolyte and cathode material by investigating the reaction process and the electrolyte's degradation on the surfaces of NCM and LCO cathode materials. Analytical methods including Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimetry paired with Gas Chromatography (DSC-GC) and Thermogravimetric Analysis combined with Gas Chromatography (TGA-GC), are utilized to access fire safety limits when interacting electrolyte with cathode materials during charging and discharging. In the first phase, the reaction mechanisms of different ionic salts such as LiPF₆, LiBF₄, and LiTFSI with carbonate solvents (DEC, DMC, EMC, and FMC etc.) in the electrolyte are investigated to highlight fire safety issues. In second phase, it is necessary to understand the heterogenous reaction occurring at electrolyte and cathode interfaces during battery cyclic. Moreover, it examines the electrolyte degradation on the surfaces of specific cathode materials such as lithium cobalt oxide (LCO) and nickel cobalt manganese oxide (NCM), using electrochemical testing, density functional theory (DFT), and chemical kinetic calculations. This review supports developing new chemical kinetic modeling and low temperature & pressure experimental studies to evaluate compatibility of electrolytes and cathode materials for improving fire safety of lithium-ion batteries.