Study on the evolution of internal resistance and entropy-thermal coefficients during the aging process of lithium-ion traction batteries

• This study reveals the correlation between internal resistance and entropy-thermal coefficients in traction batteries. • The entropy-thermal coefficient plays a crucial role in heat generation and thermal management. • Variations in internal resistance and entropy-thermal coefficients under different conditions inform battery optimization for efficiency and durability. The relationship between internal resistance and entropy-thermal coefficients significantly influences the thermal behavior and performance of traction batteries. This study systematically investigates four types of traction batteries under varying state of charge (SOC) (0%–100%) and temperature conditions (-20°C to 55°C), analyzing their entropy-thermal coefficients and internal resistance variations. Experimental results reveal that entropy-thermal coefficients exhibit non-linear changes with SOC, where values range from -1.2 mV/K to 2.8 mV/K, directly impacting heat generation. Additionally, internal resistance varies significantly with SOC and temperature, increasing by over 300% in low-temperature conditions compared to room temperature. These findings highlight the necessity of adaptive thermal management strategies considering both internal resistance and entropy-thermal coefficients, provide new insights for optimizing battery thermal behavior and lifespan by integrating dynamic entropy-thermal models into battery management systems.