High-performance sodium acetate trihydrate-based composite phase change materials for thermal management in power batteries: An experimental study

A sodium acetate trihydrate composite phase change material was prepared by melt blending for passive battery thermal management. The selected formulation containing 4 wt% expanded graphite (EG) exhibited a differential scanning calorimetry (DSC) onset temperature of 50.79°C, latent heat of 202.18 J/g, and thermal conductivity of 1.59 W/(m·K). Following macroencapsulation with a nominal 2 mm silicone layer, EM-CPCM4 retained 99.91% of its initial mass after 5 h at 70°C without visible leakage; long-term leakage prevention remains unverified. At 35°C ambient temperature, tests with one independently assembled module per configuration (n = 1) yielded a maximum cell-surface temperature of 50.32°C at 1.5 C. The corresponding 15.32°C rise was 50.1% and 27.4% lower than under natural and forced air cooling, respectively, with a maximum sensor-to-sensor temperature spread of 3.16°C. Over five consecutive cycles on the same module, maximum temperature and spread reached 53.32°C and 4.76°C, respectively. Because internal composite temperature and liquid fraction were unmeasured and the 50.32°C cell-surface maximum was below the DSC onset, the response is interpreted as proof-of-concept thermal regulation through sensible heat buffering and EG-assisted heat spreading; latent-heat contributions remain unquantified.