Improved energy storage property of ferroelectric polymer-based sandwiched composites interlayered with graphene oxide @ SiO.sub.2 core-shell nanoplatelets

The dielectric capacitors with high energy storage capability are demand for power electronic devices to keep pace with the development of the modern electronic and electrical industry. Although polymer-based dielectric composites showing the superiorities of ease processing, self-healing and low cost have a great potential in various applications, their energy storage capability is still severely limited by the negative coupling effect between dielectric permittivity and breakdown strength. In this study, we present a two-dimensional graphene oxide@silica core-shell nanoplatelets (GO@SiO.sub.2) constructed through the classical Stöber method. Moreover, a series of polyvinylidene fluoride (PVDF)/GO@SiO.sub.2/PVDF sandwich-structured composites were assembled layer-by-layer and obtained through combining the spray coating and solution casting procedures. The GO@SiO.sub.2 nanoplatelets were closely aligned and orientated along the direction that perpendicular to the electric field, forming the non-traditional inorganic middle layer. The thickness of the middle layer is dependent on the GO@SiO.sub.2 loading fraction, which directly influenced the overall dielectric and electrical performances of the sandwich-structured composites. An enhanced breakdown strength (~ 253 MV m.sup.-1) and discharged density (~ 5.19 J cm.sup.-3) can be obtained from the PVDF/GO@SiO.sub.2/PVDF composite filled with the GO@SiO.sub.2 loading fraction as small as 1.37 wt%, which are 23.4% and 161% higher than those of neat PVDF (~ 1.99 J cm.sup.-3 at 205 MV m.sup.-1), respectively. The improved energy storage capability could be attributed to the synergetic contribution of highly insulating SiO.sub.2 shell, the additional core-shell interfacial interaction, the orientation that perpendicular to electric field and the multilayered construction of composite. Thus, this research provides a promising approach for the design of advanced composites with an improved dielectric energy storage property.