Enhanced energy storage performances of nanocomposites with elaborate PN junction in core-shell structured nanofillers

Generally, the dielectric breakdown takes places as the amounts of free electrons surpasses a threshold, therefore, suppressing the amounts of free electrons and the secondary impact-ionized electrons at high electric field might enhance the breakdown strength (Eb) as well as energy storage performances of nanocomposites. Herein, core-shell structured Ni(OH)2@TiO2 (N@T for short) nanofillers were successfully designed and fabricated, where a built-in electric field is formed in PN junctions at the interface between Ni(OH)2 and TiO2. As a result, kinetic energies of electrons could be suppressed, and thus the number of free electrons and the secondary impact-ionized electrons would be reduced. Both experimental results and theoretical analyses demonstrate N@T nanofillers could increase the polarization and Eb and decrease leakage current simultaneously, resulting in the largest Ud of 20.1 J/cm3 and magnificent η of 77.5% in the 2 vol% N@T/P(VDF-HFP) nanocomposite. This work might demonstrate a novel solution to design the high-energy-density nanocomposites.