Impact of innovative cold welding techniques on the thermo-electrochemical performance of battery modules: A thermal simulation model approach

Analyzing factors affecting battery performance and discharge temperature distribution is critical for ensuring the operations of power vehicles. This analysis assesses battery lifespan, efficiency, thermal safety, and functionality across varying environmental conditions. This study investigates the impact of voltage, temperature distribution, and constant voltage charging time (CVT) on battery pack performance and degradation behavior, utilizing cold welding technology. A thermal simulation model, incorporating a user-defined function (UDF) based on a heat source, is developed to analyze the temperature distribution. First, the actual capacity is analyzed by examining the voltage distribution within the battery pack, while the temperature uniformity of the battery is evaluated for both series and parallel configurations. Second, cyclic testing is conducted to investigate the degradation behavior of the battery pack by monitoring the changes in voltage, CVT, and internal resistance. Third, a thermal simulation model is employed to simulate and analyze the temperature field of the battery pack, with an internal short-circuit point introduced to simulate thermal runaway (TR). Theexperimental results indicate that the 3P3S-c battery pack exhibits superior voltage consistency, attributed to reduced contact resistance and improved contact uniformity in the cold-welded module, resulting in a 4% increase in actual capacity. The 3P3S-c battery pack demonstrates superior temperature uniformity among the batteries. During the cycling process, the rise in internal resistance accelerates the transition to the constant voltage (CV) phase. This outcome leads to a progressive increase in CVT. Consequently, the discharge capacity of the battery pack decreases monotonically with CVT, which serves as a reliable indicator for estimating the battery’s state of health (SOH). The battery pack’s performance is constrained by its weakest cell, with 3P3S-h degrading faster than 3P3S-c under identical operating conditions. Simulations reveal that the maximum temperature in the 3P3S-h configuration occurs at the negative electrode. However, the 3P3S-c battery pack exhibits a peak temperature of 1.5°C, which is lower than that of the 3P3S-h battery pack. This trend is attributed to the welding of the negative electrode to the shell. In TR simulations, parallel batteryconfigurations exhibit faster TR than series configurations. The 3P3S-c battery pack demonstrates a delayed TR onset, attributed to the design of the negative electrode.Results from the TR simulation highlight that TR progresses more rapidly in seriessetups, while the 3P3S-c pack experiences a slower onset. These findings offervaluable insights and theoretical foundations for enhancing the performanceimprovement and thermal safety management of power battery packs, ultimatelycontributing to improved safety performance in power vehicles.