Study of flexible nanodielectric materials (FNDMs) with high permittivity is one of the most active academic research areas in advanced functional materials. FNDMs with excellent dielectric properties are demonstrated to show great promise as energy-storage dielectric layers in high-performance capacitors. These materials, in common, consist of nanoscale particles dispersed into a flexible polymer matrix so that both the physical/chemical characteristics of the nanoparticles and the interaction between the nanoparticles and the polymers have crucial effects on the microstructures and final properties. This review first outlines the crucial issues in the nanodielectric field and then focuses on recent remarkable research developments in the fabrication of FNDMs with special constitutents, molecular structures, and microstructures. Possible reasons for several persistent issues are analyzed and the general strategies to realize FNDMs with excellent integral properties are summarized. The review further highlights some exciting examples of these FNDMs for power-energy-storage applications.

Flexible Nanodielectric Materials with High Permittivity for Power Energy Storage

Dramatic changes in the physical properties of composites occur when filler particles form a percolating network through the composite, particularly when the difference between the properties of the constitutive phases is large. By use of electric conductivity and dielectric properties as examples, recent studies on the physical properties of composites near percolation are reviewed. The effects of geometric factors and intrinsic properties of the fillers and the matrix, and especially of the interface between fillers and matrix, on electric and dielectric properties near percolation are discussed. Contact resistivity at the interface is less desirable for enhancing electrical conductivity. By contrast, an interface with high resistivity suppresses tunneling between adjacent fillers and leads to percolative composites with higher dielectric constant but lower dielectric loss. This review concludes with an outlook on the future possibilities and scientific challenges in the field.

Physical Properties of Composites Near Percolation

Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

Graphite nanoplatelets (GNPs) are a type of graphitic nanofillers composed of stacked 2D graphene sheets, having outstanding electrical, thermal, and mechanical properties. Furthermore, owing to the abundance of naturally existing graphite as the source material for GNPs, it is considered an ideal reinforcing component to modify the properties of polymers. The 2D confinement of GNPs to the polymer matrix and the high surface area make the GNP a distinctive nanofiller, showing superiorities in modification of most properties, compared with other carbon nanofillers. This review will summarize the development of polymer/GNP nanocomposites in recent years, including the fabrication of GNPs and its nanocomposites, processing issues, viscoelastic properties, mechanical properties, electrical and dielectric properties, thermal conductivity and thermal stability. The discussion of reinforcing effect will be based on dispersion, particle geometry, concentrations, as well as the 2D structures and exfoliation of GNPs. The synergy of GNPs with other types of carbon nanofillers used as hybrid reinforcing systems shows great potential and could significantly broaden the application of GNPs. The relevant research will also be included in this review.

Review on polymer/graphite nanoplatelet nanocomposites

With the development of flexible electronic devices and large-scale energy storage technologies, functional polymer-matrix nanocomposites with high permittivity (high-k) are attracting more attention due to their ease of processing, flexibility, and low cost. The percolation effect is often used to explain the high-k characteristic of polymer composites when the conducting functional fillers are dispersed into polymers, which gives the polymer composite excellent flexibility due to the very low loading of fillers. Carbon nanotubes (CNTs) and graphene nanosheets (GNs), as one-dimensional (1D) and two-dimensional (2D) carbon nanomaterials respectively, have great potential for realizing flexible high-k dielectric nanocomposites. They are becoming more attractive for many fields, owing to their unique and excellent advantages. The progress in dielectric fields by using 1D/2D carbon nanomaterials as functional fillers in polymer composites is introduced, and the methods and mechanisms for improving dielectric properties, breakdown strength and energy storage density of their dielectric nanocomposites are examined. Achieving a uniform dispersion state of carbon nanomaterials and preventing the development of conductive networks in their polymer composites are the two main issues that still need to be solved in dielectric fields for power energy storage. Recent findings, current problems, and future perspectives are summarized.

1D/2D Carbon Nanomaterial‐Polymer Dielectric Composites with High Permittivity for Power Energy Storage Applications

Modified carbon nanotube composites with high dielectric constant, low dielectric loss and large energy density

Graphene-based visible light photocatalysts have been actively pursued in recent years due to the high charge mobility of graphene and hence, the lower recombination rate of electron–hole pairs. BiFeO3 with a band gap in the visible range is considered a promising candidate as an oxide photocatalyst. In this contribution, BiFeO3–graphene nanohybrids are fabricated via facile hydrothermal treatments. The morphology and band structure of BiFeO3 are modulated by graphene. Nanohybrids with BiFeO3 nanocrystallites of ∼100 nm uniformly decorated on graphene nanosheets are successfully synthesized, which exhibit a band gap of ∼1.78 eV. Chemical bonding between BiFeO3 and graphene is characterized by XPS analysis. Significant enhancement in the visible light photocatalytic performance is achieved in the BiFeO3–graphene nanohybrids. The rate for the photo-degradation of Congo Red under visible light is six times that for BiFeO3 particles, which is attributed to the combined effects of modulated band gap and covalent bonding between BiFeO3 and graphene.

Significant enhancement in the visible light photocatalytic properties of BiFeO3–graphene nanohybrids

Self-orientation of graphite-nanoplates induces anisotropy of nanoplates-epoxy composites

The invention discloses a polymer-based material with high density of energy storage and a preparation method thereof, pertaining to the technical field of the preparation of dielectric materials and energy storage materials The polymer-based material with high density of energy storage comprises carbon nanotube materials and polymer matrix materials which are modified with organics by a chemical method in the proportions of 3 wt percent to 10 wt percent, and has the effects of good compatibility with the matrix, reduction in the leakage current density of the materials and dielectric loss and improvement of the dielectric constant and the breakdown field strength of the materials The matrix material is polystyrene which is dissolved with ethyl acetate and then blended with modified carbon nanotube solution; the solution is then cast into a mould and the mould is formed by hot pressing and shaped by cold pressing The polymer-based material with high density of energy storage of the invention is characterized by good insulation, low density, excellent toughness, low cost and easy processing, and can be applied to dielectric materials of electronic devices of information technologies, dielectric projects, electrostatic storage and capacitors

Polymer-based high energy storage density material and preparing method thereof

The invention belongs to the technology field of composite materials, more particularly relates to a high dielectric composite material containing fillers with a core-@-shell structure and a production method thereof. The composite material contains 10-45 wt% of aluminum and 55-90 wt% of polystyrene. The production method comprises the following steps: subjecting aluminum powder to surface passivation treatment to obtain fillers with a core-@-shell structure, preparing ethyl acetate solution of polystyrene, adding the treated aluminum powder into the ethyl acetate solution at different mass fractions, stirring, casting, sun-drying, oven-drying, molding and shaping to obtain the high dielectric composite material containing fillers with core-@-shell structure. An oxide coating is formed on the surface of the aluminum powder after the surface passivation treatment, so as to efficiently avoid the formation of leakage conductance due to mutual contact between eclectically-conducting additives and thereby to reduce the dielectric loss of the material. The composite material has high dielectric constant, low density and good flexibility. The production method of the composite material has the advantages of simple and controllable process, low hot-pressing temperature, energy conservation and environmental protection.

Cheng Yang

Papers

Modified carbon nanotube composites with high dielectric constant, low dielectric loss and large energy density

Significant enhancement in the visible light photocatalytic properties of BiFeO3–graphene nanohybrids

Self-orientation of graphite-nanoplates induces anisotropy of nanoplates-epoxy composites

Polymer-based high energy storage density material and preparing method thereof

Highly dielectric composite material containing core-shell structured packing and preparation method thereof