Electrothermal Dynamics and Electrical Equivalent Circuit Modeling of Li-ion Batteries with NMC, NCA, and LFP Electrode Chemistries

This research aims to elucidate the intricate electrical and thermal characteristics of lithium-ion batteries under varying electrode types, encompassing Lithium Iron Phosphate (LFP), Lithium Nickel Manganese Cobalt Oxide (NMC), and Lithium Nickel Cobalt Aluminium Oxide (NCA).The experimental investigations were meticulously conducted employing two distinct methodologies: constant current discharge and pulse current discharge.Furthermore, a novel modeling technique was introduced, entailing the utilization of an electrical equivalent circuit model.The findings of this study reveal a complex, non-linear correlation between the quantity of charge and the open-circuit voltage (OCV) throughout the discharge progression.It was observed that the State of Charge (SOC), OCV, and terminal voltage (Vt) undergo alterations in a synchronous manner, albeit in a non-linear fashion.Particularly noteworthy is the observation that the LFP demonstrated a comparatively minimal fluctuation in voltage when juxtaposed with the NMC and NCA, all at changing of equivalent SOC levels.The generation of heat remained relatively uniform throughout the discharge process, exhibiting escalated rates when the SOC levels plummeted below 0.2 or escalated beyond 0.8.Regarding the electrodes, it is notable that the NMC variant showcased the highest rate of heat generation, with NCA and LFP in close succession.In the chapter concerning modeling, the suggested model demonstrated a noteworthy level of precision in predicting Vt values for SOC within the range of 1.0 to 0.2.The mean error margin was determined to be 0.004404 V, equivalent to 1.176% for NMC, -0.0256 V, corresponding to 1.126% for NCA, and -0.07 V, representing 2.601% for LFP.