MgAl LDH nanosheets loaded with Ni nanoparticles: a multifunctional filler for improving the energy storage performance of PVDF-based nanocomposites.

ABSTRACT

Polymer-based dielectric nanocomposites as raw materials of dielectric capacitors used in advanced electronics and electrical systems have a great application prospect but remain a huge challenge to energy storage performance in high electric fields. In this work, MgAl layered double hydroxide (MgAl LDH) nanosheets loaded with Ni nanoparticles were designed and synthesized, and incorporated into polyvinylidene fluoride (PVDF) to fabricate Ni-MgAl LDH/PVDF nanocomposites with high energy density. The effect of Ni-MgAl LDH nanosheet content (0.2 to 0.8 wt%) on the energy storage performance of MgAl LDH/PVDF nanocomposites was studied. As a result, after adding 0.6 wt% Ni-MgAl LDH nanosheets, the nanocomposites obtained the highest energy density 23.87 J cm-3 (at 640 kV mm-1) and the charge-discharge efficiency reached 65%, which was 76% and 18% higher than that of pure PVDF, respectively. This improvement could be attributed to the multiple functions of Ni-MgAl LDH nanosheets under an applied electric field. On the one hand, Ni nanoparticles on the surface of the MgAl LDH nanosheets could enhance the interfacial conductivity, form plenty of parallel micro-capacitors and produce Coulomb blockade effect, which resulted in high dielectric constant and high breakdown strength. On the other hand, two functions contributed by MgAl LDH nanosheets, homogenizing the electric field and inhibiting the growth of the electric tree coming from its medium dielectric constant and sheet structure, were beneficial to increase the breakdown strength. Furthermore, finite element simulations were employed to explain the mechanism of improved dielectric properties of the Ni-MgAl LDH/PVDF nanocomposites.