Simultaneous enhancement of discharge energy density and efficiency in the PMMA and PVDF blend films via introducing the Ni(OH)2 nanosheets

The progress of dielectric capacitors with superior energy storage density ( U e ) has drawn widely attentions in recent years. However, most studies improve the U e at the cost of their energy storage efficiency ( η ), which greatly limits their practical applications. In this study, a nanocomposite film based on the nickel hydroxide (Ni(OH) 2 ) and the polymethylmethacrylate and polyvinylidene fluoride blend polymer (PMMA/PVDF) is designed and prepared ( x vol%-Ni(OH) 2 -PMMA/PVDF). It has been found that introducing Ni(OH) 2 and PMMA into ferroelectric PVDF is not only able to improve the dielectric constant and breakdown field, but also able to suppress the dielectric loss and leakage current density of nanocomposite films, leading to enhanced U e and η simultaneously. Furthermore, the finite element simulation was adopted to demonstrate the mechanism of compatible improvement on the dielectric constant and breakdown field in the nanocomposite films, respectively. An excellent U e of 14.5 J/cm 3 and η of 71.7% are realized in the 3 vol%-Ni(OH) 2 -PMMA/PVDF nanocomposite film at 445 MV/m. The significantly improved U e in this composite is 181% higher than that of the pristine PMMA film and 250% higher than that of the pure PVDF film. Thus, this study might provide a new path to design the nanocomposite films with high U e and η simultaneously.