Importance of thermophysical properties of composite phase change materials in reducing lithium-ion battery temperature: a numerical and statistical approach

Abstract Lithium-ion batteries are widely utilized in many applications where energy storage is substantial, such as electric vehicles and electrical devices. Temperature is a critical factor limiting the performance, safety, and lifespan of lithium-ion batteries, particularly under high discharge rates. Phase change materials are widely used for battery thermal management; however, their low thermal conductivity restricts their effectiveness in practical applications. In this study, an expanded graphite-enhanced RT44HC composite phase change material was applied to a lithium iron phosphate prismatic battery to investigate the influence of key thermophysical properties on thermal performance. A combined numerical–statistical approach was employed, integrating electrochemical–thermal modeling with Taguchi design and variance analysis under different operating conditions (2C–3C discharge rates and 30–35 °C ambient temperatures). The results quantitatively revealed that thermal conductivity was the dominant parameter, contributing more than 95–98% to temperature reduction across all cases. In contrast, density and specific heat capacity exhibited secondary effects, while latent heat showed negligible influence under most conditions. Moreover, the maximum contribution of thermal conductivity reached 97.91% at 35 °C and 3C discharge rate. Due to the p value of latent heat being 0.0043, there was a statistically significant relationship between the latent heat and battery temperature for only the battery thermal management system operated at 35 °C and 3C discharge rate. These findings demonstrate that heat transfer in composite phase change material systems was primarily governed by conduction rather than latent heat storage under the investigated parameter ranges. The novelty of this study lies in providing a statistically validated, quantitative ranking of thermophysical properties, offering new insights beyond the predominantly qualitative conclusions. The results contribute to the design of more effective phase change material-based battery thermal management systems by identifying the most influential parameters under realistic operating conditions.