Nanocomposite Capacitors Research Articles

High-Density Capacitive Energy Storage in Low-Dielectric-Constant Polymer PMMA/2D Mica Nanofillers Heterostructure Composite

The ubiquitous, rising demand for energy storage devices with ultra-high storage capacity and efficiency has drawn tremendous research interest in developing energy storage devices. Dielectric polymers are one of the most suitable materials used to fabricate electrostatic capacitive energy storage devices with thin-film geometry with high power density. In this work, we studied the dielectric properties, electric polarization, and energy density of PMMA/2D Mica nanocomposite capacitors where stratified 2D nanofillers are interfaced between the multiple layers of PMMA thin films using two heterostructure designs of the capacitors, PMMA/2D Mica/PMMA (PMP) and PMMA/2D Mica/PMMA/2D Mica/PMMA (PMPMP). The incorporation of a 2D Mica nanofiller in the low-dielectric-constant PMMA leads to an enhancement in the dielectric constant, with ∆ε ~ 15% and 53% for PMP and PMPMP heterostructures at room temperature. Additionally, a significant improvement in discharged energy density was measured for the PMPMP capacitor (Ud ~ 38 J/cm3 at 825 MV/m) compared to the pristine PMMA (Ud ~ 9.5 J/cm3 at 522 MV/m) and PMP capacitors (Ud ~ 19 J/cm3 at 740 MV/m). This excellent capacitive and energy storage performance of the PMMA/2D Mica heterostructure nanocomposite may inform the fabrication of thin-film, high-density energy storage capacitor devices for potential applications in various platforms.

Enhanced Energy Storage in PVDF-Based Nanocomposite Capacitors through (00l)-Oriented BaTiO3 Single-Crystal Platelets.

Flexible nanocomposite dielectrics with inorganic nanofillers exhibit great potential for energy storage devices in advanced microelectronics applications. However, high loading of inorganic nanofillers in the matrix results in an inhomogeneous electric field distribution, thereby hindering the improvement of the energy storage density (Ue) of the dielectrics. Herein, we proposed a strategy that utilized (00l)-oriented barium titanate (BT) single-crystal platelets to fabricate trilayered nanocomposite dielectrics for energy storage applications. The trilayered nanocomposites consisted of two high-permittivity layers of (Ta2O5, Al2O3) codoped TiO2 nanoparticles (Ta-Al@TiO2 nps) dispersed in a poly(vinylidene fluoride) (PVDF) matrix to facilitate large electric displacement and a middle layer of (00l)-oriented BT single-crystal platelets to provide high breakdown strength. Hence, the trilayered PVDF/Ta-Al@TiO2 nps/BT single-crystal platelet nanocomposite film attains an outstanding Ue of 16.9 J cm-3 at 370 kV mm-1, which is ∼625% higher than that of the single-layer PVDF/Ta-Al@TiO2 nps film. Finite element simulation further clarified that the successive inner layer of highly (00l)-oriented BT single-crystal platelets could effectively restrain the propagation of electrical treeing in trilayered nanocomposites. This research offers an effective approach for developing flexible dielectric capacitors with an excellent energy storage performance.

Reinforced PEO/Cs polymers blend with Al2O3/TiO2 hybrid nanofillers: Nanocomposites for optoelectronics and energy storage

This work focuses on the meticulous preparation and characterization of polyethylene oxide (PEO)/chitosan (Cs) polymer blends infused with aluminum oxide nanoparticles (Al2O3 NPs) and sol-gel synthesized titanium oxide nanoparticles (TiO2 NPs). Employing the casting method, the study delves into a comprehensive analysis of the structural, optical, electrical, and dielectric properties exhibited by the resulting PEO/Cs-Al2O3/TiO2 nanocomposites. Structural evaluations utilized transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). UV–Vis spectra showed enhanced optical properties, with the indirect optical energy gap decreasing from 5.23 eV to 5.01 eV for blends with 2.4 wt% Al2O3/TiO2 NPs. The AC conductivity of the polymeric nanocomposites showed enhanced values compared with the pure blend. Additionally, dielectric permittivity and modulus exhibit tunability, presenting advantageous prospects with varying Al2O3/TiO2 NPs concentrations in the PEO/Cs blend. The Nyquist plots reveal distinctive features, including semicircular arcs at the low-frequency part and an inclined spike at the high-frequency part, with decreasing arc radius corresponding to increasing nanofiller contents. These observations are best fitted to two models of equivalent circuits. The engineered PEO/Cs-Al2O3/TiO2 nanocomposite capacitor showed enhanced storage capacity and controlled conductance characteristics. The findings of this study revealed that these nanocomposites hold promise as bandgap tuners, optical sensors, permittivity-tunable nanodielectrics, and novel host matrices for the development of solid polymer flexible electrolytes, thereby contributing to the next generation of energy storage and conversion devices with superior performance.

Effects of Film Confinement on Dielectric and Electrical Properties of Graphene Oxide and Reduced Graphene Oxide-Based Polymer Nanocomposites: Implications for Energy Storage

2D nanofillers such as graphene oxide (GO) and reduced GO (rGO)-based polymer nanocomposites have emerged as crucial materials for various applications, from flexible solid-state capacitors to electromagnetic interference (EMI) shielding devices. Specifically, the dielectric breakdown strength (EBD) and dielectric constant of polymer nanocomposite capacitors determine their ability to store energy, whereas frequency-dependent loss is crucial for EMI shielding applications. The miniaturization of energy storage and electronic devices demands a detailed understanding of the behavior of these polymer nanocomposites in the thin-film regime (micron to sub-micron thicknesses). In this work, we demonstrate the effect of confinement on the dielectric, electrical, and capacitive energy storage properties of the polyvinylidene fluoride (PVDF)–GO and PVDF–rGO films. We show that the dielectric permittivity is significantly impacted by the nanofiller confinement in thin (≈1 μm) PVDF polymer films, which is comparable to the lateral dimension of these 2D nanofillers. In thin PVDF–GO films, the nanofillers (and associated surface dipoles) become oriented quasi-parallel to the film interfaces, affecting the relative projected area to the applied electric field. The conductivity and loss tangent values increased as a function of frequency with reduced film thickness, which is beneficial to EMI shielding application. The EBD of the confined GO-based films was found to be relatively independent of the filler fraction, whereas rGO-based films increased with the filler fraction after an initial decrease. These results provide fundamental insights into rational design principles for using ultrathin GO and rGO-based polymer nanocomposite films in next-generation flexible electronic and energy storage devices.

The role of electron extinction in the breakdown strength of nanocomposite capacitors

A first-principles theory of electrical breakdown in nanocomposite capacitors, which considers the trapping and scattering (extinction) of electrons originating from the presence of nanoinclusions in the polymer matrix, is developed. The breakdown strength relative to its value for a neat polymer is expressed in terms of two parameters, one of which is determined by the volume density of the nanoinclusion polarizability and the other one is proportional to the electron trap surface density around an inclusion, while the effect of electron scattering is shown to be insignificant. A comparison of the theoretical predictions with diverse experimental data demonstrates an excellent agreement and suggests an effective tool for the design of nanocomposite capacitors.

Layer-by-layer printable nano-scale polypropylene for precise control of nanocomposite capacitor dielectric morphologies in metallised film capacitors

• A novel technique to fabricate capacitors with nano-scale layer-by-layer printing • Polypropylene gel inks were used to successively print layers as thin as 200 nm • Layer thickness is easily controllable, and the capacitance is highly predictable • Incorporation of BaTiO 3 nanoparticles was demonstrated in a structured dielectric • Presents pathway to the commercial printing of structured nanocomposite capacitors Nanocomposite dielectrics are an increasingly important area of innovation in capacitor research as an avenue to improve capacitive energy density, electrical breakdown strength, and temperature stability of devices. In such devices, morphology control is critical in order to optimise electrical field distribution in the device and to prevent the clustering of nanoparticles lowering breakdown voltages. However, this is difficult to achieve with large-scale fabrication techniques, such as melt extrusion and stretching, as melt processing can induce clustering and offers few possibilities for fine structure control of length scales below 1 µm. Layer-by-layer fabrication offers a potential bottom-up alternative whereby dielectrics are printed by successive depositions of ultra-thin layers of a room-temperature-stable polymer ink. This would allow fine thickness and morphology control and could easily be adapted to industrial-scale printing techniques, like roll-to-roll slot-die coating. This study explores this technique by developing two polypropylene-based inks in industry-friendly solvents that are then used to fabricate capacitor devices. A gel ink was able to be used to deposit ultrathin (sub-200 nm) layers of mostly amorphous polypropylene with high reproducibility. Capacitors based on these polypropylene layers perform commensurate with commercial devices, exhibiting excellent self-clearing and breakdown performance. Successive depositions of the ink were also demonstrated, allowing the fabrication of devices with finely tuned thicknesses and capacitances, as well as nanocomposite capacitors. This demonstrates the viability of layer-by-layer dielectric printing at large scale and paves the way for commercial ultra-thin conformable polypropylene capacitors, multi-component sandwich nanocomposite capacitors, and multilayer polypropylene capacitors, as well as brand new possibilities in dielectrics research.

Theoretical investigation of the nanoinclusions shape impact on the capacitance of a nanocomposite capacitor

A first-principles theoretical approach to the effective dielectric permittivity of a nanocomposite, which contains nanoinclusions dispersed in a host dielectric enclosed between two parallel metallic electrodes, is developed. The inclusions are modeled by spheroids, and their response to the external electric field is found using the point dipole approximation and Green’s function approach. As a result, besides the mutual interactions between the induced dipoles, the local field in the nanocomposite contains also a contribution from the dipole field reflected from the capacitor electrodes. It is shown that the nanocomposite dielectric permittivity is determined by an average inclusion polarizability density, and its dependence on the aspect ratio and orientations of inclusions is found analytically and investigated. The theoretical predictions derived in the paper are in excellent agreement with the available experimental data and can be used for a proper design of nanocomposite capacitors.

Theory of Electrical Breakdown in a Nanocomposite Capacitor

The electrostatic field in a nanocomposite represented by spherical nanoparticles (NPs) embedded into a dielectric between two parallel metallic electrodes is derived from first principles. The NPs are modeled by point dipoles which possess the polarizability of a sphere, and their image potential in the electrodes is found using a dyadic Green’s function. The derived field is used to obtain the parameters which characterize the electrical breakdown in a nanocomposite capacitor. It is found, in particular, that for relatively low volume fractions of NPs, the breakdown voltage linearly decreases with the volume fraction, and the slope of this dependence is explicitly found in terms of the dielectric permittivities of the NPs and the dielectric host. The corresponding decrease in the maximum energy density accumulated in the capacitor is also determined. A comparison with the experimental data on the breakdown strength in polymer films doped with BaTiO3 NPs available in the literature reveals a dominant role of the interface polarization at the NP-polymer interface and an existence of a nonferroelectric surface layer in NPs. This research provides a rigorous approach to the electrical breakdown phenomenon and can be used for a proper design of nanocomposite capacitors.

How to determine the capacitance of a nanocomposite capacitor

The theory of the effective dielectric function of a nanocomposite dielectric disposed between the metallic electrodes in a capacitor is developed from first principles. Following the Maxwell Garnett approach, the spherical nanosized inclusions in the dielectric are modeled by point dipoles and the electromagnetic field of the induced dipoles reflected from the electrodes is taken into account using the dyadic Green’s function. The developed theory substitutes the Maxwell Garnett approximation for nanocomposites in the subwavelength regime, which is realized in electrical engineering.

Recent Advances in the Synthesis of Polymer-Grafted Low-K and High-K Nanoparticles for Dielectric and Electronic Applications.

The synthesis of polymer-grafted nanoparticles (PGNPs) or hairy nanoparticles (HNPs) by tethering of polymer chains to the surface of nanoparticles is an important technique to obtain nanostructured hybrid materials that have been widely used in the formulation of advanced polymer nanocomposites. Ceramic-based polymer nanocomposites integrate key attributes of polymer and ceramic nanomaterial to improve the dielectric properties such as breakdown strength, energy density and dielectric loss. This review describes the “grafting from” and “grafting to” approaches commonly adopted to graft polymer chains on NPs pertaining to nano-dielectrics. The article also covers various surface initiated controlled radical polymerization techniques, along with templated approaches for grafting of polymer chains onto SiO2, TiO2, BaTiO3, and Al2O3 nanomaterials. As a look towards applications, an outlook on high-performance polymer nanocomposite capacitors for the design of high energy density pulsed power thin-film capacitors is also presented.

Strategic Customization of Polymeric Nanocomposites Modified by 2D Titanium Oxide Nanosheet for High‐k and Flexible Gate Dielectrics

Organic polymer-based dielectrics with intrinsic mechanical flexibility and good processability are excellent candidates for the dielectric layer of flexible electronics. These polymer films can become even more rigid and electrically robust when modified through cross-linking processes. Moreover, the composites formed by dispersing nanoscale inorganic fillers in a polymer matrix can exhibit further improved polarization property. However, these strategies can be challenging as homogeneous dispersion of nanomaterials in the matrix is difficult to achieve; thus, degradation of electrically insulating properties of nanocomposite layers is often observed. Here, a high-k, pinhole-free, and flexible poly(vinyl alcohol) (PVA)-based nanocomposite dielectric is presented, incorporating 2D TiO2 nanosheets (NSs) for the first time. Despite the attractive dielectric constant, exceptional flexibility, and electrically insulating property of PVA-TiO2 nanocomposites, only few studies on these materials have been reported. The organic/inorganic nanosheet hybrid layer, which reaches an unprecedentedly high dielectric constant of 43.8 (more than four times higher than that of cross-linked PVA), also exhibits an outstanding leakage current density as low as 10-9 A cm-2 . Furthermore, the repeated bending tests for nanocomposite capacitors reveal their capability of operating without any deterioration of their performances even after 1000 iterations of bending cycles at a bending radius of 3mm.

Enhancement thermal stability of polyetherimide-based nanocomposites for applications in energy storage

Improving thermal stability of high-performance polymer-based nanocomposite films for electrical energy storage is essential to meet ever-increasing demands for the electrical industry, especially at harsh environment applications. Here, the polyetherimide (PEI)-based composites films are prepared via grafting method in the presence of SrTiO3 (ST) nanofillers to substantially improved capacitive performances at elevated temperature. The composites films with the optimized filler compositions show a high discharged energy density of 6.76 J/cm3 under 600 MV/m at room temperature. Meantime, excellent high-temperature discharged energy density of 6.6 J/cm3 at 100 °C for the composites films is also achieved, which is superior to most of the previously reported. The simulations further demonstrate that the ST nanoparticles embedded into the composites films could effectively improve heat dissipation in comparison with pristine PEI matrix, resulting in enhancement high-temperature energy storage capabilities. This work gives considerable promise for high energy density polymer-based nanocomposite films capacitors under harsh environments.

Directly-Patternable Bi2O3 Nanoparticle for Polymer Nanocomposite Capacitor

A polyvinylidene fluoride (PVDF) film incorporating size-controlled, uniformly dispersed, directly patterned Bi2O3 nanoparticles was developed to achieve a high-k polymer nanocomposite capacitor. The photochemical metal-organic deposition (PMOD) method was employed to form uniformly dispersed and directly patterned nanoparticles on the substrate. Bi nanoparticles were produced by spin coating a Bismuth 2-ethylhexanoate solution on a Pt substrate with UV irradiation for 1, 4, 7, and 10 min. The average diameter of nanoparticles and the number of nanoparticles per unit area (μm2) were about 30, 70, and 120 nm and 30, 30, and 31 particles/μm2 for UV irradiation times of 4, 7, and 10 min, respectively. In addition, the capacitance of PVDF nanocomposite film could be controlled by the Bi2O3 nanoparticle size. The PVDF nanocomposite film containing Bi2O3 nanoparticles with 1, 4, 7, and 10 min UV irradiation were able to improve capacitance by about 1.4, 2.0, 2.7, and 3.4 times compared with an as-prepared PVDF film. By using a mask aligner, directly pattered Bi nanoparticles on the substrate, which had a 5 μm line width pattern, were successfully defined and demonstrated.

Electrochemical properties of tricalcium aluminate hexahydrate − reduced graphene oxide nanocomposites for supercapacitor device

Abstract In this study, the influence of reduced graphene oxide (rGO)−Tricalcium Aluminate Hexahydrate (C3AH6) cement nanocomposites on electrochemical properties was investigated. The rGO-C3AH6 nanocomposite samples with various of rGO laoding, such as, C3AH6_rGO-1, 3, 5, 7, 10 and 20 wt.% were easily synthesized by a rapid cement hydration method. The maximum specific surface area and average pore size diameters were 74.20 m2/g and 11.72 nm for C3AH6_rGO-20%. The charge tranfering in C3AH6_rGO nanocomposites was described using band alignments model occurring between C3AH6 and rGO. Interestingly, the increasing of both dielectric property and stability in frequency of C3AH6_rGO composite samples can be explained by the high density of free electron charges on the rGO surface. Moreover, the electrochemical properties of C3AH6_rGO electrodes had excellent capacitive properties displaying the storage charge mechanism of a hybridsupercapacitor behavior. The large rGO content of the C3AH6_rGO nanocomposite capacitor with electrolyte interfaces showed excellent electrochemical performance. The highest value of 80.479 F g − 1 was obtained from C3AH6_rGO-20% at a current density of 0.2 A g − 1 with cycling stability of 96.51% after 1000 cycles.

Negatively Charged Nanosheets Significantly Enhance the Energy-Storage Capability of Polymer-Based Nanocomposites.

Polymer-based dielectric materials play a key role in advanced electronic devices and electric power systems. Although extensive research has been devoted to improve their energy-storage performances, it is a great challenge to increase the breakdown strength of polymer nanocomposites in terms of achieving high energy density and good reliability under high voltages. Here, a general strategy is proposed to significantly improve their breakdown strength and energy storage by adding negatively charged Ca2 Nb3 O10 nanosheets. A dramatically enhanced breakdown strength (792 MV m-1 ) and the highest energy density (36.2 J cm-3 ) among all flexible polymer-based dielectrics are observed in poly(vinylidene fluoride)-based nanocomposite capacitors. The strategy generalizability is verified by the similar substantial enhancements of breakdown strength and energy density in polystyrene-based nanocomposites. Phase-field simulations demonstrate that the further enhanced breakdown strength is ascribed to the local electric field, produced by the negatively charged Ca2 Nb3 O10 nanosheets sandwiched with the positively charged polyethyleneimine, which suppresses the secondary impact-ionized electrons and blocks the breakdown path in nanocomposites. The results demonstrate a new horizon of high-energy-density flexible capacitors.

Hydrothermal synthesis of BaTiO3 nanowires for high energy density nanocomposite capacitors

One-dimensional inorganic high-k nanowires (NWs) show a potential of achieving high energy densities in polymer-matrix nanocomposite capacitors. In this study, we investigate a hydrothermal synthesis of BT NWs, by which BT NWs with high aspect ratios of pure phase, [110]-oriented structures were obtained. The BT NWs are filled in a polyvinylidene fluoride (PVDF) matrix to prepare nanocomposites and their dielectric and energy storage properties are investigated. An enhanced dielectric constant of er ~ 58 at 100 Hz is achieved in PVDF–BaTiO3 NWs (30 vol%), while the value is 47 for a traditional composite filled with BT nanoparticles (NPs). Besides, high breakdown strength of Eb > 362 MV/m is also achieved in the composites. PVDF–BaTiO3 NWs nanocomposite exhibits a high discharged energy density of Ud ~ 12.85 J/cm3 at 300 MV/m at 100 Hz with a discharge efficiency of 58%. The simulation from the finite element analysis on distributions of voltage and electric displacement is studied and showed the consistency with experimental results. This study demonstrates a facile and large-scale route to the synthesis of BaTiO3 NWs for making high er, Eb and Ud nanocomposite capacitors.

Few-layer boron nitride nanosheets exfoliated with assistance of fluoro hyperbranched copolymer for poly(vinylidene fluoride-trifluoroethylene) nanocomposite film capacitor

The polymer film capacitor has been widely applied in electronics and stationary power system due to the large power density and graceful dielectric reliability. The current requirements for flexible film capacitor are mainly on the development of polymer nanocomposite with high energy density and charge-discharge efficiency during applied electric field. Here we employed the fluoro hyperbranched polyethylene-graft-poly(trifluoroethyl methacrylate) (HBPE-g-PTFEMA) copolymer to exfoliate the boron nitride nanosheets (BNNSs) in low-boiling-point solvent, and then, the flexible poly(vinylidene fluoride-trifluoroethylene) (P(VDF-CTFE)) nanocomposite film incorporated with BNNSs was prepared by the simple solution casting. The stable BNNSs dispersion was obtained with assistance of fluoro hyperbranched copolymer as the stabilizer, which was adsorbed on the nanosheets via the noncovalent CH-π interaction against aggregation. The presence of fluoro segments improves the compatibility of BNNSs/P(VDF-CTFE) nanocomposite, which contributes to the large interfacial polarization. The energy density in 0.4 wt% nanocomposite achieves 6.8 J/cm3 with charge-discharge efficiency of 66% at 300 MV/m, which is ascribed to the large content of electroactive phase and the enhanced interfacial polarization. The fluoro hyperbranched copolymer functionalized BNNSs/P(VDF-CTFE) nanocomposite film exhibits high electric storage capability as well as lightweight feature and flexibility, which is benefit to potential applications for portable and implantable electrical devices where both the weight and size are primary concerns.

Nanocomposite Capacitors in Power Electronics and Multiferroics: Prospects for the Future of Nanopackaging and Beyond

Nanocomposites are of great interest to electronic packaging, and the opportunities are readily comprehended. First is the ability to integrate materials cheaply, with better performance, miniaturization, and reliability for a wide range of applications, including embedded passives (capacitors, resistors), low-k materials, adhesives (electrically conductive adhesives), interconnects, and thermal interface materials [1].

Simultaneously enhanced discharge energy density and efficiency in nanocomposite film capacitors utilizing two-dimensional NaNbO3@Al2O3 platelets.

With rapid developments in the consumer electronics market, electrostatic capacitors need to store as much energy as possible within a rather restricted space. In this work, nanocomposite films combining two-dimensional core-shell NaNbO3@Al2O3 platelets (2D NN@AO Ps) and poly(vinylidene-fluoride hexafluoropropylene) (P(VDF-HFP)), featuring excellent energy storage capability, high efficiency, and ultrafast discharge performance, are designed and fabricated. Both the experimental results and finite element simulations confirm the superiority of these 2D NN@AO Ps nanocomposite films in improving the breakdown strength (Eb) and energy storage capability. In particular, the introduction of 3 vol% 2D NN@AO Ps results in much enhanced discharge energy density of 14.59 J cm-3 and outstanding discharge efficiency of 70.1% in NN@AO Ps/P(VDF-HFP) nanocomposite films, which is much greater than that of pure P(VDF-HFP) (7.74 J cm-3). The corresponding nanocomposite films exhibit excellent reliability in energy storage performance under consecutive cycling. Therefore, this research could reveal a new chapter in the study and application of polymer nanocomposites in energy-storage dielectric capacitors.

Core–Shell Nanostructure Design in Polymer Nanocomposite Capacitors for Energy Storage Applications

The ability to tune the interfacial layer in nanocomposites is attracting increasing interest due to its wide application in the field of nanoscale energy storage materials. However, most of the current interfacial modifiers are flexible coils collapsing on the surface of fillers. The interfacial layer thickness cannot be readily tailored. This work demonstrates an inspiring approach to design the interfacial layer of BaTiO3 nanowires and nanoparticles with poly{5-bis[(4-trifluoro-methoxyphenyl)oxycarbonyl]styrene} (PTFMPCS). The PTFMPCS is a kind of fluoric-liquid-crystalline polymer (LCPs) that possesses polymer-chain rigidity and an orientated structure, which is useful to design the interfacial layer thicknesses of fillers. Four types of BaTiO3@PTFMPCS nanostructures are prepared and incorporated into a polymer matrix for capacitor applications. The experimental results show that the PTFMPCS interfacial layer thicknesses are precisely controlled and in good agreement with the theoretically predicted t...