P(VDF-HFP)-based nanocomposites with elaborative PN-junction nanofillers displaying high energy storage performance

Given its wide application ranges, dielectric capacitors have garnered extensive attentions. However, due to the excessive premature agglomeration of free electrons, capacitors with nanocomposites as dielectrics fail to attain high breakdown strength (Eb), and thereby constrain their ability to achieve superior energy storage performances. To alleviate the effects of free electrons and secondary impact-ionized electrons (SIE) on Eb and leakage currents, here, a novel organic-inorganic core-shell Ni(OH)2@PDI (N@P) nanofiller with opposite double-PNjunction was well-designed and successfully synthesized by coating p-typed Ni(OH)2 nanosheets with n-typed perylene diimide (PDI). It could reduce free electron kinetic energy and mitigate SIE amounts regardless of the applied electric field direction. Furthermore, PDI, as an organic compound, can uniformly and densely coat onto surfaces of 2D Ni(OH)2, as well as enhance compatibilities between Ni(OH)2 and matrix, and thereby reducing structure defects at their interfaces. Last but not the least, Ni(OH)2 nanosheets also contribute to Eb improvement via acting as scattering centers. Experimental and simulation results concurrently affirmed positive influences of organic-inorganic N@P nanofillers on discharge energy density (Ud) and efficiency (i) of P(VDF-HFP)-based (PVH-based) nanocomposites. Remarkably, 1.3 vol% N@P/PVH achieves a high Ud of 21.7 J/cm3 and i of 81.2 % under 569.0 MV/m. More importantly, it maintains an excellent energy storage performance throughout 104 cyclic tests. This study presents a valid strategy for concurrently improving Ud and i of polymer-based nanocomposites.