Experimental Study on Pyrolysis Kinetics and Thermal Stability of Li (Ni_1/3Co_1/3Mn_1/3)O₂ Cathode Material at Different State of Charge

The combination of thermogravimetric analysis, fourier transform infrared spectroscopy analysis and mass spectrometry (TG-IR-MS) are used to explore the kinetic characteristics and thermal stabilities of Li(Ni1/3Co1/3Mn1/3)O2 (NCM111) cathode under different states of charge (SOC). The sequence and amount of gas products generated during the thermal decomposition of cathode material are identified through thermogravimetric analysis combined with the FTIR spectrum and mass spectrometry. It is found that the amount of oxygen generation is proportional to SOC. In addition, Fraser-Suzuki function is used as a deconvolution method to separate the overlapped reaction process. The kinetic analysis of the major reaction stage is carried out. Results show the higher the SOC, the lower the activation energy. X-ray diffraction tests reveals that the structural stability of the cathode is weaken by the increase of SOC. The micro-calorimeter tests indicate that the thermal stability of coexist system decreases with the increase of SOC. This research can provide valuable information for the research on the thermal runaway mechanism of lithium-ion batteries and battery safety design.