Experimental evaluation of heat conduction enhancement and lithium-ion battery cooling performance based on h-BN-based composite phase change materials

Abstract

Rechargeable lithium-ion power battery is generally regarded as one of the most ideal power components for electric vehicles (EVs), on which effective thermal management can contribute to extending the service life of the battery pack and the safety of the EVs. Compared with traditional complex liquid cooling strategies, phase change materials (PCMs) are low-cost, simple, have a high latent heat and almost constant temperature during the phase change process, which is considered to be more beneficial for the cooling of the battery pack. In this work, considering the insulation of the battery pack and the low thermal conductivity of organic PCM, a thermally conductive electrically insulating composite phase change materials (C-PCMs) based on hexagonal boron nitride (h-BN)/ Paraffin (PA)/ High density polyethylene (HDPE)/ Diatomaceous (DM) was formulated and developed. Then, two 18,650 type battery packs with the parameters of 10.8v9Ah (3 series 3 parallel) were fabricated, and the C-PCM cooling and natural cooling were compared under different environment temperatures and different discharge rates (1C, 2C, 3C). The results show that the thermal conductivity of C-PCM reaches a maximum value of 2.498 W·m−1·K−1, when spherical h-BN fillers with a particle size of 30 μm/40 μm are mixed into C-PCM at a ratio of 1:1, which was 12.49 times that of pure PA. In addition, experimental results on the cooling performance of the battery pack with constant current discharge show that the cooling performance of the battery modules was enhanced by C-PCM cooling compared to natural cooling solutions. the battery pack maximum temperature (Tmax) of the C-PCM cooling module was only 48.6 °C, while the maximum temperature difference (ΔTmax) between the cells could be controlled at 2.47 °C. In general, it can be concluded that the h-BN enhanced C-PCMs module exhibited excellent temperature control and temperature uniformity of the battery pack.