This review provides a detailed overview on the latest developments in the design and control of the interface in polymer based composite dielectrics for energy storage applications. The methods employed for interface design in composite systems are described for a variety of filler types and morphologies, along with novel approaches employed to build hierarchical interfaces for multi-scale control of properties. Efforts to achieve a close control of interfacial properties and geometry are then described, which includes the creation of either flexible or rigid polymer interfaces, the use of liquid crystals and developing ceramic and carbon-based interfaces with tailored electrical properties. The impact of the variety of interface structures on composite polarization and energy storage capability are described, along with an overview of existing models to understand the polarization mechanisms and quantitatively assess the potential benefits of different structures for energy storage. The applications and properties of such interface-controlled materials are then explored, along with an overview of existing challenges and practical limitations. Finally, a summary and future perspectives are provided to highlight future directions of research in this growing and important area.

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Interface design for high energy density polymer 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

High-k polymer nanocomposites with 1D filler for dielectric and energy storage applications

Room-temperature cured hydrophobic epoxy/graphene composites as corrosion inhibitor for cold-rolled steel

We develop a simple approach to fabricate graphene-loaded TiO2 thin films on glass substrates by the spin-coating technique. Our graphene-loaded TiO2 films were highly conductive and transparent and showed enhanced photocatalytic activities. More significantly, graphene/TiO2 films displayed superhydrophilicity within a short time even under a white fluorescent light bulb, as compared to a pure TiO2 film. The enhanced photocatalytic activity of graphene/TiO2 films is attributed to its efficient charge separation, owing to electrons injection from the conduction band of TiO2 to graphene. The electroconductivity of the graphene-loaded TiO2 thin film also contributes to the self-cleaning function by its antifouling effect against particulate contaminants. The present study reveals the ability of graphene as a low cost cocatalyst instead of expensive noble metals (Pt, Pd), and further shows its capability for the application of self-cleaning coatings with transparency. The promising characteristics of (inexpen...

Superhydrophilic Graphene-Loaded TiO2 Thin Film for Self-Cleaning Applications

Novel polyaniline decorated reduced graphene oxide (rPANI@rGO) two-dimensional (2D) hybrids sheets were successfully prepared by in situ polymerization of aniline on graphene oxide (GO) sheets and successive reduction by hydrazine. PANI is heavily reduced, thus it is electrically insulating. The hybrid sheets were used as a novel filler for high performance poly(methyl methacrylate) (PMMA) nanocomposites. Our results show that, when compared with the PMMA/rGO composites, the PMMA/rPANI@rGO nanocomposites not only show a high dielectric constant but also have low dielectric loss. For example, at 1000 Hz, a dielectric constant of 40 and a dielectric loss of 0.12 were observed in the PMMA/rPANI@rGO nanocomposite with rGO/PMMA volume ratio of 6%, whereas the dielectric constant and dielectric loss of PMMA/rGO composite with rGO/PMMA volume ratio of 6% are about 20 and 1250, respectively. More importantly, the dielectric properties of PMMA/rPANI@rGO nanocomposites can be tuned by controlling the addition of the hybrid sheets. The improved dielectric properties in PMMA/rPANI@rGO nanocomposites should originate from the isolation effect of rPANI on the rGO in PMMA matrix, which not only improves the dispersion of rGO but also hinders the direct electrical contact between rGO. This research sets up a novel route to polymer composites with high dielectric constants and low dielectric loss, and also expands the application space of graphene-based fillers.

http://www.rsc.org/suppdata/jm/c2/c2jm34683d/c2jm34683d.pdf

Fabrication of two-dimensional hybrid sheets by decorating insulating PANI on reduced graphene oxide for polymer nanocomposites with low dielectric loss and high dielectric constant

Novel poly(methyl methacrylate) (PMMA) nanocomposites with high dielectric constant and low loss were successfully fabricated by using sandwich-structured polyaniline-graphene-polyaniline (rPANI-GS-rPANI) hybrids sheets as fillers. The hybrid sheets were obtained by two steps: aniline was first in situ polymerized on both surfaces of graphene oxide (GO) sheets and then the PANI-GS-PANI sheets were reduced by hydrazine. The fully reduced hybrid sheets were denoted as rPANI-GS-rPANI, which exhibit an insulator-conductor-insulator sandwich structure. It was found that, the rPANI-GS-rPANI based PMMA nanocomposites not only have high dielectric constant but also show a low loss. For instance, the dielectric constant and dielectric loss of the nanocomposite are around 28 and 0.05 at 1 MHz, respectively, when the volume ratio of GS to PMMA is 6 vol%. This study not only provides a new way to prepare polymer nanocomposites with high permittivity and low dielectric loss, but also expands the application space of graphene based fillers.

Sandwich-structured polyaniline-graphene-polyaniline two-dimensional hybrid sheets for polymer nanocomposites with high dielectric constant and low dielectric loss

Mi Li

Papers

Fabrication of two-dimensional hybrid sheets by decorating insulating PANI on reduced graphene oxide for polymer nanocomposites with low dielectric loss and high dielectric constant

Sandwich-structured polyaniline-graphene-polyaniline two-dimensional hybrid sheets for polymer nanocomposites with high dielectric constant and low dielectric loss