Enhanced high-temperature energy storage density in P-type NiOx quantum dots and P(VDF-HFP) composite dielectrics

The harsh application environment poses higher requirements for the operating temperature of dielectric energy storage capacitors. Suppressing carrier transport at high temperatures is a key method to increase the breakdown field strength (E_b) and the operating temperature of dielectrics. In this paper, low-concentration P-type semiconductor nickel oxide quantum dots (NiO_x QDs) were surface modified with polydopamine (PDA) and introduced into the polymer matrix, with the aim to capture hot carriers by constructing hole traps, thereby increasing the high-temperature E_b and energy storage density (U_dis) of the polymer. The results confirmed the efficiency of the strategy. At 90 °C, the E_b of the NiO_x@PDA/P(VDF-HFP) film reached 2242.78 kV/cm, and the U_dis reached 2.94 J/cm³, which were 42.41 % and 164.86 % higher than those of the pure P(VDF-HFP) film. Thermal and mechanical analyses indicated that the enhanced E_b and U_dis were mainly attributed to the restriction of the Poole-Frenkel emission within the dielectrics. Together with the enhanced compatibility of the organic-inorganic composite interface, the macro defects of the composites were further suppressed and electrical properties were further increased. This work offers a straightforward and efficient approach for manufacturing high-temperature energy storage dielectrics.