Oxygen vacancy-induced deep trap states in Ni(OH)2 nanosheets for enhanced dielectric energy storage

Here, oxygen vacancy was introduced into hexagonal β-Ni(OH) 2 (NV) nanosheets to prepare poly (vinylidene fluoride-co-hexafluoropropylene)-based dielectric composites. Oxygen vacancy gradients were controlled, and the enhanced effects on energy storage performance were systematically investigated. It was found that the oxygen vacancy elevated the Ni 2+ /Ni 3+ ratio, shifted the Fermi level downward and induced formation of deep trap states. The moderate oxygen vacancies produced uniformly distributed deep strap states, which delayed the carrier migration by the capture-release mechanism. The Fermi level (E v − E f ) of NV 1.5 was 1.064 eV and showed the smallest energy separation from the valence-band, resulting in the highest interfacial potential barrier and inhibiting the charge injection. So, the oxygen vacancy obviously affected leakage current, breakdown strength and energy density. It was observed that leakage current density of the composites reduced to 3.48 × 10 −8 A/cm 2 . At the 0.3 wt% loading of NV1.5, the composite achieved a breakdown strength of 792.97 kV/mm and an energy density of 21.15 J/cm 3 (88.17 % over the matrix), with charge–discharge efficiency of 74.12 % and below 1 % performance degradation after 10 4 cycles. This work establishes a novel route based on defect engineering for dielectric storage materials at the atomic level. Download: Download high-res image (101KB) Download: Download full-size image