Thermal kinetics comparison of delithiated Li[NixCoyMn1-x-y]O2 cathodes

Abstract Layered Li[NixCoyMn1-x-y]O2 (NCM) cathodes with high capacity are poor in thermal stability and cause safety concerns on their batteries. Although the thermal features of various NCM materials have been widely described, detailed kinetics for thermal modeling still remain unknown. Here, we conducted thermal stability tests and for the first time quantified the thermal kinetics related to the three-stage phase transition process of the delithiated NCM cathodes with different nickel contents and particle structures. Results show that NCM cathodes with higher nickel ratios and polycrystal (PC) structures display worse thermal stability. Enhancing nickel contents from 0.33 to 0.8 leads to a 50 °C drop in the first thermal reaction temperature and up to 60% decrease in the activation energy, with enthalpy two times larger. The influence of particle structure is less significant. PC materials show up to a 10% drop in activation energy, with total enthalpy increasing by 25 J when compared with single-crystal materials. Finally, the thermal kinetics are combined with a widely-used battery thermal runaway (TR) model. The model simulation results predict the battery TR tipping point at x = 0.5. The detailed kinetics obtained in this study can further contribute to the development of battery thermal models and prompt the applications of NCM materials.