Ultrahigh Breakdown Strength and Improved Energy Density of Polymer Nanocomposites with Gradient Distribution of Ceramic Nanoparticles

Abstract

High‐energy‐density polymer nanocomposites with high‐dielectric‐constant ceramic nanoparticles as the reinforcement exhibit great potential for energy storage applications in modern electronic and electrical systems. However, the decline of breakdown strength by high loading of ceramic nanoparticles hinders this composite approach from sustainable promotion of energy density. In this work, an approach is proposed and demonstrated by constructing gradient distribution of the spherical ceramic nanoparticles in the polymer matrix. These gradient‐structured nanocomposites possess remarkably improved mechanical and electrical behaviors, which give rise to ultrahigh breakdown strength and much‐promoted energy density. Moreover, this enhancement effect can be further enlarged via increasing the grades number of gradient structures. This work provides an effective strategy for developing flexible high‐energy‐density polymer/ceramic nanocomposites for dielectric and energy storage applications.

Enabling High‐Energy‐Density High‐Efficiency Ferroelectric Polymer Nanocomposites with Rationally Designed Nanofillers

“…Even more impressively, an ultrahigh η of 83.4% at 700 MV m −1 is achieved in the solution‐processed P(VDF‐HFP) composite with Al 2 O 3 NPLs. To our knowledge, this value not only far exceeds those obtained in solution‐processed ferroelectric polymer nanocomposites (Figure 4c,d) [ 25,26,35,50–61 ] but also outperforms the highest values of the ferroelectric polymer nanocomposites prepared by complicated procedures, including electrostatic spinning of composite precursors, [ 30–32,40 ] post‐synthetic modification of nanostructured fillers, [ 33,34,36 ] and mechanical press of multi‐layered films processes with multiple steps, [ 33,62 ] as summarized in Table S4, Supporting Information. Intriguingly, as summarized in Figure 4c, the ferroelectric polymer nanocomposites containing low‐ K fillers such as BNNS with K composite / K matrix <1 normally exhibit η of <78%, [ 25 ] whereas the nanocomposites loaded with high‐ K fillers such as BaTiO 3 with K composite / K matrix value >1 generally have η of <70%.…”

“…Poly(vinylidene fluoride) (PVDF)‐based ferroelectric polymers are considered as the most promising class of dielectric materials for high‐energy‐density capacitors because of their largest K , that is, >10 at 1 kHz, among the current dielectric polymers. [ 19–24 ] To further improve K and the breakdown strength of ferroelectric polymers, a variety of nanostructured fillers ranging from wide‐bandgap boron nitride nanosheets (BNNSs) [ 25–27 ] and semiconductors [ 28,29 ] such as titanium dioxide (TiO 2 ) and tantalum pentoxide (Ta 2 O 5 ) to high‐ K perovskite ceramics [ 30–34 ] including barium titanate (BaTiO 3 ), barium strontium titanate (BaSr x Ti 1−x O 3 ), and barium zirconium titanate (BaZr x Ti 1−x O 3 ) have been introduced into PVDF and its binary and ternary polymers. For example, Li et al.…”

“…fabricated a class of ferroelectric copolymer nanocomposites with topologically distributed BaTiO 3 nanoparticles, which exhibit a discharged energy density ( U e ) of 18 J cm −3 and a charge–discharge efficiency (η = U e / U c × 100%) of 65% at an applied field of 670 MV m −1 . [ 30 ] The spatially arranged BaTiO 3 nanofiber‐based copolymer composites deliver a U e of 25.5 J cm −3 with a η of 76.3% at 690 MV m −1 . [ 31 ] The PVDF nanocomposite with BNNS‐wrapped BaTiO 3 nanoparticles displays an E b of 580 MV m −1 and an U e of 17.6 J cm −3 .…”

Structure design boosts concomitant enhancement of permittivity, breakdown strength, discharged energy density and efficiency in all‐organic dielectrics

“…When the outer layer content was 20 vol.%, they achieved a favourable energy density of 18.8 J/cm 3 and the finite element method simulation revealed the interfaces between two different layers could block the development of electrical trees, which accounts for the much higher breakdown strength. With the development of fabrication technics, researchers expanded the sandwich structure to multilayer structure [35][36][37][38][39] and even gradient structure [26,40,41]. Zhu et al utilised the multilayer coextrusion technics to investigate a number of polymer films with a multilayer structure, such as PC/ P(VDF-HFP) [35,36], PSF/PVDF [37].…”

Tuning ferroelectricity of polymer blends for flexible electrical energy storage applications

“…The polymer blend film with the 80 vol% P(VDF-TrFE)/20 vol% PMMA composition and commercial biaxial oriented polypropylene (BOPP) film were charged by an electric field of 200 MV m −1 and then discharged to a load resistor of 100 kΩ. The discharged time is determined as the time that 90% of the maximum energy density is discharged [40,41]. As shown in Fig.…”