Nacre-Mimetic Multifunctional Aramid Dielectric Paper Enabled by Percolated 3D Boron Nitride Networks and Interfacial...

The widespread adoption of aramid dielectric paper as core insulation in advanced motor systems is undermined by its intrinsically low thermal conductivity (λ), which promotes localized hotspot formation and precipitates insulation failure under severe thermoelectrical coupling stresses. However, current mainstream solutions face a restrictive trade-off between λ and other essential properties, presenting a persistent challenge for the design of thermoconductive aramid papers. Herein, we report a multifunctional aramid composite dielectric paper constructed from one-dimensional (1D) aramid nanofibers (ANFs) as the structural scaffold, synergistically integrated with hydroxyl-functionalized 1D boron nitride nanotubes (BNNTs) and 2D boron nitride nanosheets (BNNSs) as thermally conductive fillers. The composite paper features a hierarchically ordered self-assembled architecture that establishes an unobstructed 3D phonon transport network, wherein BNNTs serve as spatial bridges interconnecting isolated BNNSs. This structural synergy, coupled with robust interfacial bonding between ANFs and BNNTs as well as BNNSs, concurrently elevates the in-plane λ to 15.71 W·m-1·K-1 and the tensile strength to 283.36 MPa for the composite paper, representing 9.64-fold and 1.32-fold improvements over pristine ANF paper, respectively. Moreover, the nacre-inspired microstructure endows the composite paper with an ultrahigh breakdown strength of 349.06 kV/mm, wherein the abundant deep traps at the ANF-filler interfaces critically suppress charge carrier migration and prevent premature electrical breakdown. These multidimensional blocks design strategy offers a promising avenue for multifunctional dielectric materials tailored to the insulation systems of next-generation electrical and power equipment.