Experimental investigation on efficient thermal management of autonomous underwater vehicle battery packs using anisotropic expanded graphite/paraffin composite materials

•The anisotropic high-performance CENG/PCM composites were prepared.•The thermal conductivity of PCM has increased by more than 30 times.•The CENG/PCM were applied to thermal management of AUVs’ battery packs.•The temperature rise of the battery pack with CPCM has decreased by 29.9 %.•The available mass energy density of battery packs increases by 63.55 %. The thermal safety issue of battery packs is very prominent in the field of electrically powered AUVs. However, there has been few previous studies for AUV battery thermal management. In this study, anisotropic high-performance CENG/PCM composite materials were prepared and their internal microstructure was characterized by SEM, XRD, Raman spectroscopy, and TEM. A modified correlation was proposed to predict the latent heat and thermal conductivity of CPCM. In addition, the systematic experimental study was conducted on the thermal management of AUV battery modules using CENG/PCM. A new criterion called available mass energy density considering the weight and temperature control performance of CENG/PCM has been proposed to evaluate the comprehensive thermal management performance of battery packs. The results show that CENG can significantly improve the thermal conductivity of PCM. When the CENG density is 0.3 g/cm3, the thermal conductivity of CENG/PCM in the perpendicular and parallel compression directions is 118.7 and 31 times higher than that of pure PCM, respectively. CENG/PCM has demonstrated excellent thermal management performance. Compared to the battery module without CENG/PCM, the maximum temperature of the battery module with CENG/PCM decreased by 29.9 % and the temperature difference decreased by 55.3 % at 2C discharge rate. The optimal thickness of CENG/PCM is recommended to be 30 mm, and when the mass of the battery module increases by 16.84 %, the available mass energy density increases by 63.55 %. The findings of this study contribute to promoting the commercial application of CENG/PCM composite materials in thermal management of autonomous underwater vehicle battery packs.