Abstract
An integrated battery model is constructed by coupling a three-dimensional electrochemical model with a two-dimensional axisymmetric heat transfer model, and implemented for simulation of the thermal behavior in a 21,700-type cylindrical cell, comprising a graphite/LiNi0.8Co0.15Al0.05O2 chemistry. The electrochemical model is based on the disassembled battery structure and considers the temperature-dependent ageing kinetics induced by solid electrolyte interphase (SEI) formation and metallic Li plating. Compared with a classic pseudo-2D (P2D) model, the proposed model provides better fitting results for both battery electrochemical and thermal properties. The simulation results show battery surface temperatures can reach up to 80 °C and 110 °C for discharge rates of 3C and 4C, respectively. By applying appropriate cooling liquids, this surface temperature increase can be efficiently controlled and the core temperature will be correspondingly reduced, while the internal temperature gradient remains the same. It is primarily the improvement of thermal conductivity in radial direction which can reduce differences between core and surface temperature. Moreover, the model is able to characterize accelerated ageing kinetics caused by battery self-heating during operation. The results show that the capacity of the investigated battery decreases to 80% after 500 cycles, which is in good agreement with commercial specifications.
Highlights
Li-ion batteries have been exploited as energy and power sources in several different kinds of electric devices, with recent years experiencing an accelerated growth in particular for the market volume of batteries for electric vehicles (EVs) due to their excellent performance and economical and environmental superiorities over other candidates [1, 2]
Dielectric liquids generally provide a lower heat transfer coefficient around 100–200 W⋅m-2 K-1 [52], but the heat transfer is on the other hand achieved on the entire area of the battery cell
This study establishes an integrated model for a cylindrical Li-ion battery cell by coupling a 3D electrochemical model with a 2D axisymmetric heat transfer model
Summary
Li-ion batteries have been exploited as energy and power sources in several different kinds of electric devices, with recent years experiencing an accelerated growth in particular for the market volume of batteries for electric vehicles (EVs) due to their excellent performance and economical and environmental superiorities over other candidates [1, 2]. The practical utilization of EV LiBs is still confronted with great challenges due to overheating and thermal runaway [3,4] if operated improperly. Operations outside of the optimal thermal window of LiBs cause rapid battery ageing, thereby causing large energy costs due to extensive cooling [5,6]. Charging/discharging LiBs with high voltage or current may generate production of heat, and if not reallocated efficiently, the battery temperature would increase. This may lead to battery capacity fade because of degradation of the cathode and accelerated solid electrolyte interphase (SEI) film growth on the anode [7,8,9]. Monitor and control of thermal behavior in LiBs is crucial, for improving battery performance and for guaranteeing their usage safety
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