Loofah-inspired anisotropic flexible phase change composite for efficient thermal management of high-rate batteries

The thermal management of high-rate charging cylindrical batteries necessitates advanced thermal management solutions capable of addressing their intrinsic anisotropic heat dissipation for ensuring both safety and operational longevity. While phase change materials (PCMs) offer passive thermal buffering, their typically low and isotropic thermal conductivity fundamentally limits their efficacy in managing directional heat flux. Inspired by the hierarchical and anisotropic skeleton of natural loofah, this study designed a hybrid carbon-based high thermally conductive dual-pathway skeleton integrating a continuous radial network of 1D carbon nanotubes (CNTs) for rapid longitudinal heat transfer with an interconnected axial channels of 3D flame-retardant expanded graphite (EG) for enhanced transverse thermal diffusion. At a low filler content of 8.0 wt%, the resulting flexible PCM composite exhibits superior axial and radial thermal conductivities of 5.96 W/(m·K) and 3.57 W/(m·K), respectively. When deployed in a 2.0C fast-charging scenario, this anisotropic PCM reduces the average temperature rise by 12.4 °C compared to the baseline battery, and by 5.2 °C compared to pure honeycomb-like EG skeleton, significantly outperforming conventional thermal management strategies. Systematic experiments and mechanistic analysis reveal that the cylindrical batteries induce dominant radial heat accumulation. This study not only provides a high-performance material solution for suppressing thermal runaway in high-power energy storage devices but also establishes a universal bio-inspired design for developing advanced thermal management composites tailored to anisotropic heat flux in next-generation electronics.