A thermally induced flexible composite phase change material with boron nitride nanosheets/carbon nanotubes modified skeleton for battery thermal management

Employing phase change materials (PCMs) has become a promising approach in the field of battery thermal management. However, low thermal conductivity, liquid phase leakage, and high rigidity still limit its widespread application. In this paper, we dispersed boron nitride nanosheets (BNNS) and multi-walled carbon nanotubes (MWCNT) as binary thermally conductive fillers onto a three-dimensional porous flexible skeleton of silanized hydrophobically modified cellulose nanofiber (SCNF) to prepare a hybrid aerogel. By employing it as a flexible carrier, a shape-stable and thermally induced flexible composite phase change material (CPCM) with binary alkanes was successfully prepared. Experimental results show that the three-dimensional porous flexible skeleton structure of the hybrid aerogel effectively avoids the leakage of PCM and maintains good flexibility during melting. The synergistic dispersion strategy based on SCNF enables the BNNS/MWCNT binary filler to bridge a perfect thermal conduction path at a low loading of 1 vol%. When the ratio of BNNS to MWCNT on the three-dimensional skeleton of SCNF is 7:3, the prepared SC/35B/15M@PCM shows the best synergistic enhancement effect of 91.8% in thermal conductivity compared with pure PCM, while maintaining a high PCM load capacity of 94.51 wt% and a high phase change latent heat level of 213.27 J/g. In addition, based on the simulation results, the prepared SC/35B/15M@PCM shows a superior temperature control effect which reduce the temperature of commercial lithium-ion batteries by 3.42 °C–16.41 °C at a discharge rate of 1-3C. The CPCM synthesized in this work achieves a balance between shape stability, energy storage density, and thermal conductivity.