Metal Oxide Reinforced/Decorated Polymers as High Permittivity Dielectrics for Energy Storage Devices

Abstract

High dielectric permittivity (high-k) materials are essential in fabricating energy storage devices, thin-film transistors, and piezoelectric devices. Solution-processable dielectrics are more desirable in energy storage film capacitors, and functional electronics, since they are cost-effective and can be produced in large quantities. The solution-process assisted by ultrasound is a well-known method as it provides the possibility of tuning properties of subsequent products by easily adjusting the precursor solutions. In this work, three categories of dielectrics, such as metal oxide-based dielectrics, namely, lanthanum cerium oxide (LCO), lanthanum zirconium oxide (LZO); polymer composite dielectrics, namely, polymethyl methacrylate (PMMA)- LZO and polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)-LZO; anisotropic dielectrics such as polystyrene-iron oxide (PS-Fe3O4) patchy particles and lanthanum oxide-zirconium oxide (La2O3-ZrO2) dumbbell-shaped Janus particles, were fabricated at low temperatures using a sonochemical approach. In polymer composites, the main emphasis was on obtaining a uniform distribution of high-k LZO filler into a PMMA and PVDF-HFP matrix to improve their dielectric permittivity and energy storage density while lowering the dielectric loss. The effect of LZO content on dielectric properties and optimum LZO loading to achieve improved energy storage density of the films was studied. The enhanced energy storage density of 5.94 J/cm3 at 63.6 MV/m breakdown strength for PMMA-LZO and 15.8 J/cm3 at 545 MV/m for PVDF-HFP/LZO have been achieved. Further, the fundamental insights into the role of the polymer-metal oxide (PS-Fe3O4 patchy particles) and metal oxide-metal oxide (La2O3-ZrO2) interfaces on the dielectric properties have been addressed by considering experimental outcomes and computational simulations. Also, a new mechanism of charge build-up at these interfaces have been proposed. Computational outcomes reveal that the creation of interface bound-charges at the interface is predominantly responsible for the improved dielectric properties. Local morphology, dispersibility, interface area, crystallinity, and ionization of the metal oxides determine the overall dielectric permittivity of the film. Polymer-inorganic interface engineering and design open up a new area to develop hybrid materials for future energy storage systems.