Radially Aligned SiO ₂ Networks in Three-Dimensional Boric Acid/Melamine/SiO ₂ Aerogel with Excellent Flame Retardant and Heat Insulation Performance for Battery Thermal Management

Developing multifunctional aerogels with simultaneously ultralow thermal conductivity, exceptional mechanical robustness, and scalable processability remains a formidable challenge for advanced thermal management in lithium-ion batteries (LIBs). Herein, we report a three-dimensional (3D) networked BMS (boric acid/melamine/SiO2) aerogel featuring radially aligned SiO2 frameworks, fabricated via an in situ sol–gel method coupled with freeze-drying. The radial alignment of SiO2 nanofibers along the preformed aerogel matrix leads to a unique three-dimensional interconnected porous architecture reinforced by synergistic Si–O–Si covalent bonds and hydrogen bonding networks. This structural design not only enhances the load-bearing capacity of the fibrous skeleton but also dramatically extends the heat transfer path for phonons and reduces solid-phase heat conduction, resulting in a low thermal conductivity of 0.0395 W/m·K and a low density of 0.0615 g/cm3. The stabilized SiO2 frameworks further improve thermal stability upon thermal decomposition of the organic components. In addition, the incorporation of phase change materials (PCMs) enhances the thermal buffering performance of the BMS aerogel without compromising its porosity, enabling a significant reduction in the battery surface temperature at discharge rates of 1.5 C and 2 C. During nine consecutive cycles of 2 C discharge, a 1 mm-thick BMS/PEG composite phase change material (cPCM) layer achieves a maximum peak temperature reduction of 5.5 °C. This work presents a robust and scalable strategy for the design of high-performance aerogel-based thermal regulators, which exhibit excellent flame retardancy and thermal insulation performance.