Flexible Regenerated Cellulose/Boron Nitride Nanosheet High-Temperature Dielectric Nanocomposite Films with High Energy Density and Breakdown Strength

Abstract

Traditional dielectric polymers are nonbiodegradable and nonrenewable petroleum-derived synthetic ones. Here, we report on flexible and 2D nanolayer-structured nanocomposite dielectric films which are easily fabricated from aqueous NaOH/urea solutions of biodegradable and renewable cellulose and boron nitride. Cellulose molecules serve as a stabilizer for exfoliated boron nitride nanosheet (BNNS) and provide the nanocomposites with a high dielectric constant, while BNNS significantly improves their breakdown voltage. Here, 10 wt % of BNNS in the nanocomposite leads to a film with energy storage density of 4.1 J cm–3 and breakdown voltage of 370 MV m–1. The energy storage density is much higher than that of any commercial dielectric polymer as well as any biomass-based materials reported in the literature. Concurrently, these nanocomposites possess high thermal conductivity of 2.97 W m–1 K–1 and excellent thermal stability of dielectric properties. This work provides a new route toward fabricating environmentally friendly biomass-based thermally stable dielectric energy storage devices.

Interface design for high energy density polymer nanocomposites

“…However, this type of sandwich-structured composite often suffers from a low relative permittivity and polarization due to the central polymer layer being of low relative permittivity, which limits the overall energy density. To overcome this issue, a small amount of ceramic nanofiller, such as NaNbO 3 platelets, 172 (Na 0.5 Bi 0.5 ) 0.93 Ba 0.07 TiO 3 platelets, 78 BaTiO 3 nanoparticles, 173 BaTiO 3 nanofibers, 162 boron nitride nanosheets (BNNs), 174,175 and BaSrTO 3 (BST) nanofibers, 115 have been incorporated into the polymer central layer to create an insulating layer with enhanced relative permittivity. As an example, Wang et al 176 presented a trilayer-structured nanocomposite prepared by hot pressing.…”

Highly Thermoconductive, Thermostable, and Super‐Flexible Film by Engineering 1D Rigid Rod‐Like Aramid Nanofiber/2D Boron Nitride Nanosheets

“…Additionally, the effectiveness can be evaluated by comparisons of in‐plane thermal conductivity enhancement per unit of filler (Figure e). ANF/BNNS nanocomposite film possesses the highest in‐plane thermal conductivity enhancement per unit filler (1.55 W m −1 K −1 wt% −1 ), superior to those of other nanocomposite films . Moreover, in comparison with some common metal materials, this film also exhibited much higher thermal conductivity per unit density than Fe (10.25 W m −1 K −1 /10 3 (kg m −3 )) and was only slightly lower than Cu (45.06 W m −1 K −1 /10 3 (kg m −3 )) and Ag (40.86 W m −1 K −1 /10 3 (kg m −3 )).…”

“…To highlight the superior thermal conductivity of our film, we also compared it with the advanced BN‐based films cited in previous studies. Clearly, our film possessed the highest conductivity values at all filler content levels . Additionally, the effectiveness can be evaluated by comparisons of in‐plane thermal conductivity enhancement per unit of filler (Figure e).…”

Sandwich-structured poly(vinylidene fluoride-hexafluoropropylene) composite film containing a boron nitride nanosheet interlayer

“…It has a high forbidden bandwidth (z6 eV) and a high intrinsic breakdown voltage. 23,24 It is widely used in research to improve the energy storage characteristics of polymer materials. For example, BNNSs are directly added to the matrix, which resulted in a signicantly improved breakdown eld strength.…”