▎ 摘　　要

Graphene nanosheets are widely employed for fabricating high-dielectric-constant polymer nanocomposites for energy storage. However, severely reduced electric breakdown strengths of composites with increasing graphene content limit their high-field applications. To improve breakdown strengths of polyvinylidene fluoride/graphene composites without sacrificing dielectric constants, in this work, we proposed a rational strategy of constructing MXene quantum dot inter-layers for preparing ternary composites with desirable electric properties, owing to inter-layer induced quantum confinement and Coulomb blockade effects. Graphene oxide@nitrogen-doped Ti3C2 MXene quantum-dot hybrid nanoparticles were synthesized via hydrogen-bond induced self-assembly route. Binary polymer/graphene and ternary polymer/hybrid-particle nanocomposite films were fabricated by solution cast process. Compared with binary composites, ternary counterparts have synergistically improved dielectric constants and breakdown strengths. Repeated disorder-bounce of electrons and strong coupling between electrons and holes, inside each quantum dot, might be responsible for superior electric performances of ternary composites. High dielectric constant (similar to 53@1 kHz) and breakdown strength (similar to 205 MV m(-1)) were realized in ternary composite with 0.12 wt % of nanoparticles. This work might pave a road for large-scale fabrication of high-performance nanocomposite dielectrics for energy storage.