High energy storage performances of P(VDF-HFP)-based nanocomposites by dual-filler synergy of carbon quantum dots and Ni(OH)2 nanosheets

Polymer dielectric capacitors are pivotal for advanced electronics, while their limited energy density ( U d ) impedes further miniaturization. Constrcution of nanocomposites to utilizing their both merits seems to improve their U d , however, conventional single-filler systems typically enhance either dielectric constant ( ε r ) or breakdown strength ( E b ), at the expense of the other. Herein,A dual-filler approach is developed to achieve concurrent enhancement of ε r and E b , thereby overcoming the trade-off limitation inherent in single-filler systems. In this study, a series of nanocomposites are designed by incorporating carbon quantum dots (C QDs) into a P(VDF-HFP) matrix with Ni(OH) 2 nanosheets (Ni(OH) 2 NSs). C QDs enhance ε r through the micro-capacitor effect and suppress electron migration via the Coulomb blockade effect. Concurrently, Ni(OH) 2 NSs act as scattering centers and barriers, extending the breakdown path to improve E b . Simulation results confirm synergistic suppression of electrical tree growth. The best nanocomposite obtains a U d of 21.9 J/cm 3 at 570.3 MV/m with charge-discharge efficiency ( η ) of 72.3%. This U d shows a 188% improvement over the single-filler counterpart. Meanwhile, excellent cyclic stability over 10 4 cycles and rapid discharge (τ 0.9  = 117 ns) are also demonstrated. This dual-filler system provides a rational route to concurrently improve ε r and E b for next-generation dielectric capacitors.