Comparison of the Thermal Reaction Kinetic Parameters of Layered Li[NixCoyMnz]O2 Cathode Material with Different Nickel Content and Different Crystal Structure

Abstract

Layered Li[NixCoyMnz]O2 (NCM) material with high nickel content is a promising cathode material for next generation lithium-ion batteries because of its high energy density. However, the NCM materials become unstable with nickel content increasing and face safety problems at elevated temperatures. In this study, we report and compare the thermal stability and thermal reaction kinetic parameters of NCM materials with different Ni content (x=0.3, 0.5, 0.7 and 0.8) and different crystal structure (single crystal / poly-crystal). The active materials were heated with differential scanning calorimetry (DSC) from room temperature to 550℃ at various heating rates. The kinetics parameters (pre-exponential factor, activation energy, mechanism function and reaction enthalpy) of each exothermic reaction were identified with Kissinger’s method and nonlinear fitting method. Results showed that the NCM crystal structure had little influence on the NCM exothermic peak temperature and the kinetic parameters. With Ni content increasing, the exothermic peaks shifted to lower temperatures and the activation energy of the first exothermic peak decreased. Thus, the NCM cathode with higher Ni content was easier to experience phase transition process accompanied with oxygen release at elevated temperatures. This study compared the thermal stability of NCM materials with different Ni content and different crystal structure, and provided kinetic parameters of the NCM exothermic reactions for the future thermal safety simulations of lithium-ion batteries. Figure 1