Synergistic topological and electronic barriers enable exceptional electrical breakdown in 1D/2D composite dielectrics

The relentless push for higher power densities and miniaturization in electronics and electrified transportation has placed stringent demands on dielectric materials, which must simultaneously conduct heat and block charge. Yet, these two functions are inherently antagonistic. The biomimetic assembly of nanoscale building blocks offers a promising route to circumvent this trade-off, yet inevitably introduces a high density of heterointerfaces whose charge dynamics remain poorly captured by conventional macroscopic models. Here, we construct highly ordered nacre-mimetic architectures from 1D aramid nanofibers and 2D boron nitride nanosheets, achieving an 80% enhancement in breakdown strength up to 371.56 kV/mm. Thermally stimulated depolarization current analysis reveals a dense population of deep-level traps with a characteristic activation energy of 1.43 eV, while first-principles calculations identify a massive 2.1 eV conduction band offset arising from interfacial charge redistribution. This combination generates a built-in electric field sufficient to impose potent potential barriers that suppress carrier injection, while the deep traps, whose microscopic origin we attribute to the non-ideal 1D/2D interface, are proposed to immobilize hot electrons and truncate avalanche breakdown. Our findings establish a synergistic physical picture where morphological ordering and electronic band engineering collectively overcome the long-standing thermal conductivity–insulation deadlock, offering a viable pathway toward robust dielectrics for next-generation high-power systems.