Effect of KH550 modification on SiC dispersion, pore structure, and thermal insulation in PVA/colloidal silica composite aerogels

Thermal runaway in lithium-ion batteries has created a growing demand for lightweight thermal-barrier materials that combine low thermal conductivity, flame retardancy, and mechanical stability. In this work, KH550-modified silicon carbide (SiC) was incorporated into poly(vinyl alcohol) (PVA)/nano-silica sol particle (NSiCP) composite aerogels by pre-freezing and freeze-drying. A Taguchi orthogonal design was first used to screen suitable formulation conditions, after which the effects of KH550 modification and modified-powder loading on particle distribution, pore-network evolution, and thermal, mechanical, and flame-retardant performance were examined. KH550 modification reduced SiC sedimentation and localized agglomeration, promoting a more continuous porous framework. Within the investigated range, increasing the modified-powder loading refined the mesopores and restricted gas-phase heat transfer while maintaining framework integrity, whereas excessive powder addition caused macroscopic cracking. Among the investigated samples, the PVA/NSiCP aerogel prepared with 6 wt% recovered KH550-modified SiC powder exhibited a density of 0.089 g cm^-3, a thermal conductivity of 34.10 mW m^-1 K^-1, and a compressive stress of 1.51 MPa at 70% strain. It also exhibited rapid self-extinguishing behavior without sustained burning or flaming drips, met the V-0 criteria under the applied vertical-burning test conditions, and showed the highest LOI of 28.80 ± 0.36% among the investigated formulations. These results establish a formulation-structure-property relationship showing that balancing surface modification and powder loading with pore refinement and framework integrity enables thermally conductive ceramic powder to be incorporated into lightweight aerogels for battery thermal-barrier applications.