Thermal Behavior and Microstructures of Cathodes for Liquid Electrolyte-based Lithium Batteries

Lithium-ion batteries are widely used as a power source for portable equipment. However, the use of highly flammable organic solvents in the liquid electrolyte component in these batteries presents a serious safety concern. In this study, the thermal stability of battery cathodes comprising LiNiMnCoO (NMC) and LiPF-based electrolyte solutions have been investigated using transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) methods. Ex situ TEM measurements revealed that significant structural change occurred in the charged NMC composite after heating at a temperature above the exothermal peaks. It was found that LiF nanocrystallites precipitated in LiPF and that a number of nanoscale stacking faults developed in the [Formula: see text] layered structure of NMC. The results suggested that the decomposition reaction of LiPF and the structural change of NMC were directly associated with the exothermic reaction in the liquid electrolyte-based NMC electrode composite.