Development of sodium acetate trihydrate-based composite phase change materials with expanded graphite for nonflammable thermal stabilization and isothermal performance in battery modules

Abstract

Phase change materials (PCMs) offer significant potential for passive thermal management of lithium-ion battery modules due to their high energy storage density and isothermal heat release. Organic PCMs, despite their widespread use, suffer from flammability and low thermal conductivity, limiting their application in battery thermal management systems. In contrast, salt hydrate-based PCMs provide excellent cost-effectiveness, high energy storage density, and non-flammability, making them highly promising. However, challenges such as phase separation, supercooling, and inappropriate phase change temperature hinder their practical application. To address these issues, this study developed a novel composite-PCM (CPCM) using sodium acetate trihydrate (SAT) as the primary PCM, with urea and potassium chloride to adjust the phase transition temperature. Disodium hydrogen phosphate and carboxymethyl cellulose were incorporated as nucleating and thickening agents, while expanded graphite (EG) was added to enhance thermal conductivity. The CPCM/EG was designed to operate within a preferred temperature range (<45 degrees C) and integrated into a battery module. Experimental results demonstrated that at an ambient temperature of 25 degrees C, CPCM/EG reduced battery surface temperature by 37.9 %, 26.2 %, and 10.5 % at discharge rates of 5C, 3C, and 1C, respectively, compared to natural air cooling, with temperature fluctuations maintained below 4.7 degrees C. The developed CPCM/EG effectively maintained battery temperature within the optimal range during high discharge rates, enhancing operational stability. Thus, the developed CPCM/EG is expected to be applicable to various fields, including passive thermal management systems for electric vehicles, renewable energy storage, and smart grid energy management systems.