Correlation of Degradation and Thermal Stability of Different Positive Active Materials in Lithium Ion Batteries

摘要

Three aspects are considered key for active materials in future lithium ion battery applications: High energy density, long cycle life, and enhanced safety properties. Beyond that, a detailed knowledge of the interactions between electrochemical performance, degradation effects and the influence on the safety properties is of fundamental importance. In this regard, the thermal decomposition of state-of-the-art positive electrode active materials is known to be strongly exothermic in presence of electrolyte, thus, triggering numerous reactions that can eventually lead to a thermal runaway. Therefore, investigations on the thermal stability of different positive electrode active materials are essential in order to develop safer lithium ion batteries that also exhibit an enhanced energy density and a prolonged cycle life. Even though different active materials have been investigated with regard to their thermal stability in the charged and discharged state, [1-2] the influence of degradation effects on the thermal stability of active materials is widely unknown. Therefore, this study correlates degradation effects and their influence on the thermal decomposition of different layered, spinel-type, and olivine-type based positive electrodes at elevated temperatures.