Elucidating in-situ heat generation of LiFePO4 semi-solid lithium slurry battery under specific cycling protocols

Abstract

Semi-solid lithium slurry battery combines the advantages of the high energy density of lithium-ion battery and the flowability of flow battery electrodes and has attracted attention in energy storage. Elucidating the heat generation during cycling is crucial for evaluating the safety. However, there is a relative lack of research in this field of semi-solid lithium slurry battery. Herein, the heat generation of lithium iron phosphate (LiFePO4) semi-solid lithium slurry battery during cycling under specific cycling protocols is investigated in this work. The results show that the battery has lower heat generation when cycling at an ambient temperature of 35–50 ℃ and a charging cutoff voltage below 4.0 V, meanwhile, it maintains considerable capacity. However, when the charging cutoff voltage exceeds 4.4 V, the cyclic heat generation of the battery increases significantly, and the capacity attenuates significantly. Meanwhile, the classical equation for calculating battery heat generation of lithium-ion battery is no longer reliable. This is mainly because the electrolyte content of the semi-solid lithium slurry battery is too high (over 80 %), and at high charging cutoff voltage, the side decomposition reactions of the electrolyte increase significantly. Subsequent characterization of electrode materials also confirms this inference. This study can provide a clearer understanding of the safety of semi-solid lithium slurry battery and has guiding implications for industrial applications.