Bio-inspired anisotropic phase-change composites via in-situ alkaline activation for thermally adaptive, anti-dripping, and electrically insulating battery thermal management

Pre-modification-free in-situ alkaline activation triggers spontaneous interfacial reconstruction between aramid and BN nanofibers. • Leaf-vein-inspired anisotropic nanocomposites establish vertical phonon highways via single-bottom directional cryogenic ice-templating. • Multi-scale capillary micro-confinement yields 1.12 W/(m·K) out-of-plane thermal conductivity and anti-dripping fire-shielding boundaries. The aggressive implementation of fast charging protocols in high-energy-density lithium-ion batteries severely intensifies internal Joule heating, triggering a hazardous electro-thermal-fire trilemma. Traditional organic phase-change materials (PCMs) offer an attractive energy-free cooling route but suffer from low thermal conductivity, liquid leakage, flammability, and poor electrical insulation. Herein, a leaf-vein-inspired anisotropic phase-change composite material (CPCM) is fabricated via an elegant, pre-modification-free in-situ alkaline activation and directional ice-templating strategy. By leveraging the residual nucleophilic hydroxyl ions natively dwelling within the strongly alkaline aramid nanofiber (ANF) slurry, the unpassivated edge defects of pristine boron nitride nanofibers (BNNFs) undergo a spontaneous interfacial chemical reconstruction. This in-situ reaction matures an extensive hydrogen-bonding network and mechanical interlocking with neighboring ANF backbones, structurally locking them into highly aligned, vertical lamellar cell walls. Benefiting from continuous vertical phonon highways, the engineered CPCM delivers an outstanding out-of-plane thermal conductivity of 1.12 W/(m·K) while preserving a premium latent heat density of 216.9 J/g with an elite cycling enthalpy retention of 96.58% across 400 continuous thermal iterations. Furthermore, the robust aerogel framework confers exceptional shape-stabilization, reliable electrical isolation (12.47 MΩ), and advanced anti-dripping structural integrity that effectively prevents hazardous flaming liquid runoff and pool fires during aggressive thermal matrix decomposition. When evaluated under a continuous 2C constant-current rapid-charging protocol for 1800 s, the dynamic synergy between accelerated directional heat conduction and large-capacity latent heat buffering successfully shunts intense internal heat flux outward, pinning the battery contact interface temperature at 34.3 °C with a peak regulation efficiency of 69.2%. Download: Download high-res image (351KB) Download: Download full-size image