Two-Dimensional High-k Nanosheets for Dielectric Polymer Nanocomposites with Ultrahigh Discharged Energy Density

Flexible dielectric materials with high electrical energy densities are of crucial importance in advanced electronics and electric power systems. The conventional methods for fabricating flexible dielectric materials with high electrical energy densities are introducing zero-, one-, and three-dimensional high-k inorganic nanofiller into a dielectric polymer matrix while less two-dimensional high-k nanofillers were included. Herein, two-dimensional (2D) high-k titanium dioxide nanosheets prepared by a one-step hydrothermal reaction were utilized to boost the energy storage performance of dielectric polymer nanocomposites. It was found that compared with the polymer matrix the nanocomposites not only exhibit an enhanced dielectric constant but also show suppressed dielectric loss, which is desirable for energy storage applications. The nanocomposite with 5 wt % 2D nanosheets exhibits a superhigh discharged energy density of 13.0 J/cm3 at 570 MV/m, which is nearly four times greater than that of commercialized biaxially oriented polypropylene (BOPP) (3.6 J/cm3 at 600 MV/m). In addition, nanocomposites with 5 wt % zero- and one-dimensional (0D and 1D) nanofiller are also fabricated for comparison. Results reveal that discharged energy densities of nanocomposites with 5 wt % 2D nanosheets are 236% and 382% higher than those of nanocomposites with 5 wt % 1D (5.5 J/cm3 at 400 MV/m) and 0D (3.4 J/cm3 at 300 MV/m) nanofiller, respectively. Finite element simulation was conducted to study the electric field distribution in nanocomposites with different shapes of nanofillers. Furthermore, the comparison of the current nanocomposites and previous reported nanocomposites with 0D, 1D, and 3D nanofillers shows that the 2D high-k nanofiller exhibited superior potential in advancing the energy storage nature of polymer nanocomposites. This remarkable exhibition of energy storage capability provides new insights into the development of high performance dielectric materials.