Gaining insight into lithium-ion battery degradation by a calorimetric approach

With the growing demand for lithium-ion batteries (LIBs) in transportation and renewable energy sectors, ensuring reliability and mitigating degradation are crucial challenges for their widespread deployment. This study investigates the relationship between thermal characteristics and degradation/reliability by developing an in-situ heat measurement methodology for LIBs operating under grid services. Using adiabatic mode-based calorimetry, we determine the thermal behavior of two commercial cells with distinct cathode chemistries (Ni-rich layered oxide and olivine) before and after two years of peak shaving operation and demonstrate a strong correlation between thermal characteristics and electrochemical performance and its degradation. By further analyzing the heat sources separation and differentiating between irreversible and reversible heat, we disclose the underlying degradation mechanisms of LIBs. These findings emphasize the critical role of thermal characteristics in determining LIB reliability and degradation, while the obtained heat data can aid in the development and calibration of LIB state-of-health models for grid applications.