(Keynote) Interplay of Aging Temperature and Thermophysical Properties of Lithium-Ion Battery Electrodes

Abstract

While it is well known that the electrochemical performance of lithium-ion batteries degrades with repeated cycling, the impact of aging on thermal properties is less well understood. Degradation of thermal transport within the cell can lead to increased or even excessive temperatures that in turn lead to accelerated ageing or even thermal runaway. Thus, understanding how aging impacts thermal properties is critical to ensuring safe and reliable operation of batteries. In this presentation, we evaluate the evolution of the thermal diffusivity, heat capacity, and density of the electrodes of lithium-ion battery cells which were aged at different thermal conditions. From the measured properties, we estimate the thermal conductivity of the electrodes and the active materials in the electrodes as well. Overall, the transport properties approximately follow a trend with the time-averaged temperature during the aging process. The changes in the thermal properties are correlated with observations of changes to the microstructure of the electrodes during cycling. These results can impact the design of battery systems for improved performance and stability throughout their lifetime.