Continuous characterization of reversible and irreversible heat of lithium-ion batteries using online electrochemical impedance spectroscopy and differential isothermal calorimetry

• Continuous characterization of LIBs’ reversible and irreversible heat is proposed. • Enhanced online EIS is optimized by multi-frequency superposition excitation. • Differential power compensation is used to improve SNR of isothermal calorimeter . • This methodology is verified through heat measurements of LFP and NCM batteries . Characterization of reversible and irreversible heat of lithium-ion batteries (LIBs) provides insights into their thermal behavior, enabling the development of optimized thermal management strategies. Conventional techniques mainly use calorimetry or electrochemical impedance spectroscopy (EIS) as separate methods, which can’t obtain the continuous curve between different heat sources and states of charge. It also requires a lengthy measurement. In this study, an enhanced online EIS based on multi-frequency superposition driver signal optimization is proposed. The signal-to-noise ratio of the isothermal calorimeter is optimized using the differential power compensation method. The enhanced online EIS is used to detect the internal resistance during the charge or discharge of the LIB while it is inside an isothermal calorimeter . This study presents the reversible and irreversible heat measurements of commercial LiFePO 4 and Li[Ni 0.5 Co 0.3 Mn 0.2 ]O 2 batteries in different environments. Experimental results indicate the accuracy and efficiency of the method in the thermal characterization of LIBs .