Ultrareliable Composite Phase Change Material for Battery Thermal Management Derived from a Rationally Designed Phase Changeable and Hydrophobic Polymer Skeleton

The development of phase change material (PCM) for battery thermal management poses key limitations on its reliability caused by leakage and shape deformation under high temperature. In this work, a kind of phase changeable and hydrophobic polymer skeleton is grown in situ in a paraffin (PA)/expanded graphite matrix to obtain the leakage-proof composite PCM (CPCM) at the kilogram-level. Benefiting from the additional latent heat provided by the phase changeable alkyl side chains of the polymer skeleton, the obtained CPCM shows a high latent heat of 120.3 J g–1 coupled with a thermal conductivity of 2.92 W m–1 K–1. Most importantly, the three-dimensional cross-linking main chain and the hydrophobic alkyl side chains endow the obtained CPCM with extraordinary shape stability under high temperatures up to 250 °C and high PA adsorbing capability, respectively. As a consequence, the CPCM presents excellent antileakage performance for the battery module (21 V/16 Ah) under harsh working conditions, i.e., 50 charge–discharge cycles at 3C–4C, thus giving rise to a durable cooling performance. The maximum temperature (Tmax) and temperature difference (ΔTmax) of the battery module can be controlled constant at 50.9 and 5.0 °C during the cycles, respectively. By stark contrast, owing to the obvious leakage phenomenon, the battery module with traditional CPCM adopting a classical low-density polyethylene skeleton shows increasing Tmax and ΔTmax during the cycles.