Microstructural evolution and thermal protection mechanism of ceramifiable silicone composites via boron phosphate phase transformation

The pervasive risk of thermal runaway propagation in lithium–ion battery energy storage stations necessitates advanced thermal barrier materials. To address this, we developed a biomimetic silicone matrix composite inspired by volcanic rock strata. This material integrates a zinc borate/black phosphorus flame–retardant system, a silica aerogel insulation network, and an aramid fiber reinforcement. Upon high–temperature exposure, the composite spontaneously forms a dense, coherent boron phosphate (BPO 4 ) ceramic layer, akin to volcanic rock, which provides exceptional thermal shielding. Experimental results demonstrate outstanding performance: the composite maintains mechanical stability from –40 to 300 °C, reduces surface temperature rise by 75% compared to pure silicone foam, and lowers the peak heat release rate and total smoke production by 52.5% and 47.9%, respectively. In simulated thermal runaway tests, it completely prevented propagation to adjacent cells and reduced mass loss by 66.1%. Mechanistic studies reveal that the performance stems from a synergistic gas–phase and condensed–phase flame–retardant action, coupled with enhanced insulation and interfacial reinforcement. This work presents a promising material solution for enhancing the intrinsic safety of Energy storage power stations.