Enhanced Energy Storage Density Research Articles

Energy storage and loss capacity of graphene‐reinforced poly(vinylidene fluoride) nanocomposites from electrical and dielectric properties perspective: A review

AbstractPolymer/graphene nanocomposites have shown promising potentials in energy storage applications due to their high permittivity, enhanced energy storage density, flexibility, and improved thermal and mechanical properties. The addition of graphene nanosheets to polymer matrix improves existing and incorporate new properties on such nanocomposites for various engineering applications. For instance, graphene nanosheets in polymer matrix are believed to form microcapacitors. Each microcapacitor contributes to the effective capacitance and dielectric constant of the composite. Although research has proved polymer/graphene composites as high dielectric constant materials, the major challenges facing their practical applications are high energy dissipation, high dielectric loss, and low electric field strength. In view of this, many researchers have shown efforts to minimize energy losses associated with polymer/graphene composites by insulating graphene nanosheets with different organic and inorganic substances. This is believed to prevent direct contact of graphene nanosheets and reduce the high mobility of π‐orbital or free electrons in the polymer matrix. However, maintaining high dielectric constant at low dielectric loss in polymer/graphene composites has not been achieved. If this challenge can be addressed in the future, polymer/graphene composites can yield energy storage capacity comparable with those of electrochemical capacitors. Therefore, this review considered energy storage and loss capacity of poly(vinylidene fluoride)/graphene nanocomposites from the perspective of electrical and dielectric properties. This article to the best of our ability reviewed various research results on dielectric constants/losses, breakdown strengths, energy densities, and electrical and thermal conductivities of poly(vinylidene fluoride)/graphene nanocomposites. Results extracted from the different published literature were tabulated and discussed at length to outline the reasons for the high dielectric loss in the neighborhood of percolation thresholds and the way forward.

In-depth understanding of interfacial crystallization via Flash DSC and enhanced energy storage density in ferroelectric P(VDF-CTFE)/Au NRs nanocomposites for capacitor application.

High-capacity or high-power-density capacitors are being actively investigated for portable electronics, electric vehicles, and electric power systems. We describe the filler system in dielectric nanocomposites with a small loading of Au nanorods [NRs] to elucidate the mechanism of interfacial crystallization behavior including the crystallization kinetics, and crystalline morphology and structure, and to investigate the intrinsic causes for concurrent great improvements in the dielectric constant and energy density in the nanocomposite system. Remarkly, at high crystallization temperature, the addition of Au NRs, which are used as heterogeneous nucleators, can reduce the nucleation barrier, resulting in accelerating the crystallization rate. However, the crystallization rate slows down at low temperatures because the addition of Au NRs limited the mobility of poly(vinylidene fluoride-chlorotrifluoroethylene) [P(VDF-CTFE)] chains, and thus enhanced the diffusion barrier. Furthermore, the addition of NRs has a huge impact on the crystalline morphology and structure which changes from large paraelectric α-phase spherulites with TGTG' conformations into minor ferroelectric γ-phase spherulites with T3GT3G' conformations, and also produces more exogenous interfaces between the lamellar crystals and amorphous regions, resulting in a higher dielectric constant and higher electric energy density in P(VDF-CTFE)/Au NRs nanocomposites. Our approach provides a facile and straightforward way to design or understand PVDF-based polymers for their practical applications in high-energy-density capacitors.

Largely enhanced energy storage density of poly(vinylidene fluoride) nanocomposites based on surface hydroxylation of boron nitride nanosheets

PVDF/OH-BNNS nanocomposites show improved dielectric, thermal and mechanical properties through cooperation with surface hydroxylated BNNSs.

P(VDF-HFP)/PMMA flexible composite films with enhanced energy storage density and efficiency

P(VDF-HFP)/PMMA composite films were fabricated using a blending and hot-molding method and investigated using both experimental and theoretical methods. The extended Flory–Huggins model were adopted to study the Gibbs energy, miscibility, and phase composition of binary mixture, and results showed favorable interactions and compatibility between P(VDF-HFP) and PMMA. The dielectric constant and loss of blend films were reduced compared to pristine films. The ferroelectric hysteresis loops of blend films are much slimmer than that of pristine P(VDF-HFP) films. The discharged energy density of 11.2 J/cm3 with the efficiency of 85.8% was obtained in the P(VDF-HFP)/PMMA blend films with 42.6 vol% PMMA at the electric field of 475 MV/m. The discharged energy density of blend film is 2.6 times of that of pristine film, while the energy storage efficiency is 2.07 times higher than that of pristine film. The origin of enhancement in the dielectric energy storage properties were analyzed using Fourier transform infrared spectra and atomistic simulation. FT-IR results showed γ–phase of P(VDF-HFP) was induced in blend films with a relative amount of 93.6%, comparing with the pristine P(VDF-HFP) films. The van der Waals forces and hydrogen bonding at the interface and the chain entanglement were responsible for the miscibility and stabilization of γ–phase, strengthening the energy storage properties.

Enhanced energy storage properties of {Bi0.5[(Na0.8K0.2)1-Li ]0.5}0.96Sr0.04(Ti1--Ta Nb )O3 lead-free ceramics

Abstract Energy storage properties of {Bi 0.5 [(Na 0.8 K 0.2 ) 1- z Li z ] 0.5 } 0.96 Sr 0.04 (Ti 1- x - y Ta x Nb y )O 3 (BNKLSTTN- x / y / z ) lead-free ceramics are investigated. It is found that Ta performs better than Nb in the case of their energy storage density values, and the addition of optimum Li contents can enhance the energy storage properties by enhancing the dielectric breakdown strength (DBS). Enhanced energy storage density of 1.60 J/cm 3 under a low electric field of 90 kV/cm is achieved in BNKLSTTN-0.025/0/0.10 samples, and the fatigue-free properties are also observed. In addition, the BNKLSTTN-0.025/0/0.10 samples show the enhanced temperature dependence of energy storage density. These results indicate that the BNKLSTTN- x / y / z ceramics are one of the most promising lead-free materials for energy storage applications.

Enhanced Energy-Storage Density and High Efficiency of Lead-Free CaTiO3-BiScO3 Linear Dielectric Ceramics.

A novel lead-free (1 - x)CaTiO3-xBiScO3 linear dielectric ceramic with enhanced energy-storage density was fabricated. With the composition of BiScO3 increasing, the dielectric constant of (1 - x)CaTiO3-xBiScO3 ceramics first increased and then decreased after the composition x > 0.1, while the dielectric loss decreased first and increased. For the composition x = 0.1, the polarization was increased into 12.36 μC/cm2, 4.6 times higher than that of the pure CaTiO3. The energy density of 0.9CaTiO3-0.1BiScO3 ceramic was 1.55 J/cm3 with the energy-storage efficiency of 90.4% at the breakdown strength of 270 kV/cm, and the power density was 1.79 MW/cm3. Comparison with other lead-free dielectric ceramics confirmed the superior potential of CaTiO3-BiScO3 ceramics for the design of ceramics capacitors for energy-storage applications. First-principles calculations revealed that Sc subsitution of Ti-site induced the atomic displacement of Ti ions in the whole crystal lattice, and lattice expansion was caused by variation of the bond angles and lenghths. Strong hybridization between O 2p and Ti 3d was observed in both valence band and conduction band; the hybridization between O 2p and Sc 3d at high conduction band was found to enlarge the band gap, and the static dielectric tensors were increased, which was the essential for the enhancement of polarization and dielectric properties.

Enhanced energy storage density of Ba0.4Sr0.6TiO3 ceramics with additive of Bi2O3-B2O3-ZnO glass

The Ba0.4Sr0.6TiO3 (BST) ceramics with Bi2O3-B2O3-ZnO (BBZ) glass additive were prepared by the solid state reaction route. Microstructural observation demonstrates that the average grain size reduces obviously with increasing glass additive. The dielectric constant decreases and the dielectric breakdown strength (BDS) increases as glass additive increases. The energy storage density of ceramics with 5wt% glass additive is 0.62J/cm3 attributed to the relatively high dielectric constant and BDS. These results indicate that this material is a promising candidate for energy storage capacitor devices.

High‐energy storage density and excellent temperature stability in antiferroelectric/ferroelectric bilayer thin films

AbstractThe antiferroelectric/ferroelectric (PbZrO3/PbZr0.52Ti0.48O3) bilayer thin films were fabricated on a Pt(111)/Ti/SiO2/Si substrate using sol‐gel method. PbZr0.52Ti0.48O3 layer acts as a buffered layer and template for the crystallization of PbZrO3 layer. The PbZrO3 layer with improved quality can share the external voltage due to its smaller dielectric constant and thinner thickness, resulting in the enhancements of electric field strength and energy storage density for the PbZrO3/PbZr0.52Ti0.48O3 bilayer thin film. The greatly improved electric breakdown strength value of 2615 kV/cm has been obtained, which is more than twice the value of individual PbZr0.52Ti0.48O3 film. The enhanced energy storage density of 28.2 J/cm3 at 2410 kV/cm has been achieved in PbZrO3/PbZr0.52Ti0.48O3 bilayer film at 20°C, which is higher than that of individual PbZr0.52Ti0.48O3 film (15.6 J/cm3). Meanwhile, the energy storage density and efficiency of PbZrO3/PbZr0.52Ti0.48O3 bilayer film increase slightly with the increasing temperature from 20°C to 120°C. Our results indicate that the design of antiferroelectric/ferroelectric bilayer films may be an effective way for developing high power energy storage density capacitors with high‐temperature stability.

Enhanced energy storage density by inducing defect dipoles in lead free relaxor ferroelectric BaTiO3-based ceramics

In this work, Mn-doped 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3 ceramics were prepared by the conventional solid state reaction method, and the effect of defect dipoles on energy storage properties of lead free relaxor ferroelectric BaTiO3-based ceramics was studied. The crystal structure, dielectric properties, and energy storage properties were explored in detail. It was found that polarization hysteresis (P-E) loops of 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3-x wt. % MnCO3 (0.2–0.5) ceramics took on high maximum polarization (Pmax) and low remanent polarization (Pr). Meanwhile, recoverable energy density (Wrec) and energy conversion efficiency (η) were obviously enhanced by inducing defect dipoles into BaTiO3-Bi(Mg2/3Nb1/3)O3 relaxor ferroelectrics. The 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3-0.3 wt. % MnCO3 ceramic was found to exhibit good energy storage properties with a Wrec of about 1.70 J/cm3 and a η ∼ 90% under an electric field of 210 kV/cm. The breakdown electric field and Wrec of BaTiO3-based materials were significantly increased in the present work, and they might be good candidates for high power energy storage applications.

High energy density in P(VDF-HFP) nanocomposite with paraffin engineered BaTiO3 nanoparticles

Dielectric materials with high energy storage density are attracting scientific and commercial interest due to the prospect of application in advanced electronic devices and electric power systems. Ceramic/polymer composite is one of the most promising materials to obtain high energy density because it combines high permittivity from ceramic and high breakdown strength as well as flexibility from polymer matrix. However, the homogeneous dispersion and compatibility of nanoparticles in polymers matrix are still of great challenges due to the different surface energy between inorganic fillers and organic polymer matrix. Interfaces modification for ceramic fillers is an effective way to ease the mentioned problems. Herein, we proposed a low-cost and environmentally friendly route to prepare a core–shell structure by paraffin engineer the BaTiO3 nanoparticles. The modified BaTiO3 nanoparticles exhibited homogeneous dispersion in the ferroelectric polymer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix and strong interfacial adhesion with the polymer matrix. The nanocomposites prepared in this work showed notably enhanced energy storage density. The maximum storage energy density of the nanocomposite with 50vol% BaTiO3 increased to 21.1J/cm3 at 150kV/mm. These results indicate that paraffin is an effective modifier to prepare high energy storage density capacitor.

Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers

There is a growing need for high energy density capacitors in modern electric power supplies. The creation of nanocomposite systems based on one-dimensional nanofibers has shown great potential in achieving a high energy density since they can optimize the energy density by exploiting both the high permittivity of ceramic fillers and the high breakdown strength of the polymer matrix. In this paper, BaTiO3 nanofibers (NFs) with different aspect ratio were synthesized by a two-step hydrothermal method and the permittivity and energy storage of the P(VDF-HFP) nanocomposites were investigated. It is found that as the BaTiO3 NF aspect ratio and volume fraction increased the permittivity and maximum electric displacement of the nanocomposites increased, while the breakdown strength decreased. The nanocomposites with the highest aspect ratio BaTiO3 NFs exhibited the highest energy storage density at the same electric field. However, the nanocomposites with the lowest aspect ratio BaTiO3 NFs achieved the maximal energy storage density of 15.48 J/cm3 due to its higher breakdown strength. This contribution provides a potential route to prepare and tailor the properties of high energy density capacitor nanocomposites.

Enhanced energy storage properties of BiAlO3 modified Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3 lead-free antiferroelectric ceramics

Lead-free (1−x)(0.75Bi0.5Na0.5TiO3–0.25Bi0.5K0.5TiO3)–xBiAlO3 (BNT–BKT–100xBA, x=0–0.10) ceramics were prepared by two-step sintering method and their phase structure, micro morphology and electrical properties were systematically investigated. X-ray diffraction analysis indicates a pure perovskite phase for x≤0.06 as well as a structural evolution from a tetragonal toward a pseudocubic phase. Transmission electron microscopy study of the x=0.04 composition reveals the existence of antiferroelectric phase with a0a0c+ oxygen octahedron tilting which is in the form of nano-domains. Polarization-electric field and current-electric field hysteresis loops demonstrate that the increase of BA concentration destroys the ferroelectric order and strengthens antiferroelectric order. A much enhanced energy storage density of 1.15J/cm3 and efficiency of 73.2% is achieved under 105kV/cm at x=0.06. In addition, its energy storage property is found to depend weakly on temperature within the measurement range of 25–150°C.

Enhanced energy storage density of 0.55Bi0.5Na0.5TiO3-0.45Ba0.85Ca0.15Ti0.85Zr0.1Sn0.05O3 with MgO addition

0.55Bi0.5Na0.5TiO3-0.45Ba0.85Ca0.15Ti0.85Zr0.1Sn0.05O3-xwt%MgO ceramics were prepared by solid state route and their phase compositions and dielectric properties were investigated with the focus on improving energy storage density for capacitor applications. The XRD data results reveal that all samples possess a pure perovskite phase and some secondary phases of MgO and Mg2TiO4 can be observed in the MgO doped samples. The frequency dispersion gradually disappears by the addition of MgO and MgO doped samples show a diffuse phase transition behavior. Dielectric breakdown strength of the samples are greatly improved with the increasing content of MgO. The sample with x = 5 shows a high dielectric breakdown strength of 18.97 kV/mm, a high discharge energy density of 1.62 J/cm3 and a high energy efficiency of 79.51%, making it most suitable for application as high energy storage density capacitors.

Enhanced energy storage properties of barium strontium titanate ceramics prepared by sol-gel method and spark plasma sintering

Dense Ba0.4Sr0.6TiO3ceramics with fine grains and uniform microstructure were prepared by sol-gel method and spark plasma sintering (SPS). The dielectric properties, microstructures, and energy storage performance of spark plasma sintered Ba0.4Sr0.6TiO3 ceramics were evaluated. Fine Ba0.4Sr0.6TiO3 powders were synthesized by sol-gel method at above 750 °C. SPS technique showed its advantages in suppressing exaggerated grain growth and increasing the relative density of Ba0.4Sr0.6TiO3ceramics. Diffuse phase transition and nearly linear P-E behavior were observed in all samples. Moderate dielectric constant (∼960), low dielectric loss (∼0.003), high electrical breakdown strength (∼240 kV/cm), significantly enhanced energy storage density (∼1.23 J/cm3) and ultrahigh energy storage efficiency (∼94.52%) were obtained in Ba0.4Sr0.6TiO3 ceramics by using sol-gel method and spark plasma sintering.

Significantly enhanced energy storage density for poly(vinylidene fluoride) composites by induced PDA-coated 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nanofibers

The significantly enhanced energy storage characteristics of 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nanofibers/PVDF dielectric composites with low doping ratios and large aspect ratio nanofillers.

Enhanced dielectric properties and energy storage density of interface controlled ferroelectric BCZT-epoxy nanocomposites

Polymer nanocomposites with ferroelectric fillers are promising materials for modern power electronics that include energy storage devices. Ferroelectric filler, Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) nanopowder, was synthesized by sol-gel method. X-ray diffraction (XRD) studies confirmed the phase purity and the particle size distribution was determined by transmission electron microscopy (TEM). Extended aromatic ligand in the form of naphthyl phosphate (NPh) was chosen for surface passivation of BCZT nanoparticles. Surface functionalization was validated by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and impedance spectroscopy using slurry technique. The dielectric constant of surface-passivated BCZT nanopowder was ~155, whereas pristine BCZT nanopowder dielectric constant could not be assessed due to high innate surface conductivity. Furthermore, BCZT–epoxy nanocomposite films were prepared and analyzed by differential scanning calorimetry (DSC), dielectric spectroscopy, dielectric breakdown strength (DBS), and scanning electron microscopy (SEM). Owning to stronger polymer–particle interface, dielectric measurements of 5 vol.% NPh surface functionalized BCZT–epoxy nanocomposites indicated improved DBS and glass transition temperature (Tg), reduced dielectric loss, and enhanced energy storage density compared to untreated BCZT–epoxy composites and pure epoxy. The energy storage density of 30 vol.% NPh surface functionalized BCZT–epoxy nanocomposite of 20 μm film thickness was almost three times that of pure epoxy polymer of identical film thickness.

Enhanced energy storage density performance in (Pb0.97La0.02)(Zr0.5Sn0.44Ti0.06)–BiYO3 anti-ferroelectric composite ceramics

(1 − x)(Pb0.97La0.02)(Zr0.5Sn0.44Ti0.06)–xBiYO3 ((1 − x)PLZST–xBYO), with x = 0.0–0.5, have been fabricated by the conventional solid-state reaction process. The phase evolution, microstructure, dielectric and energy storage properties have been investigated in detail. According to the XRD study, a secondary phase was found at room-temperature. The secondary phase was gradually increased with increasing x. The microstructure further revealed that the BYO doping leads to an increase in secondary phase. The EDS analysis revealed that Bi ions and Y ions are mainly substituted for A-site in the perovskite structure. As a result, the maximum value of energy storage density is 0.8 J/cm3, which is 2.66 times as high as that of pure PLZST ceramics.

Research Update: Enhanced energy storage density and energy efficiency of epitaxial Pb0.9La0.1(Zr0.52Ti0.48)O3 relaxor-ferroelectric thin-films deposited on silicon by pulsed laser deposition

Pb0.9La0.1(Zr0.52Ti0.48)O3 (PLZT) relaxor-ferroelectric thin films were grown on SrRuO3/SrTiO3/Si substrates by pulsed laser deposition. A large recoverable storage density (Ureco) of 13.7 J/cm3 together with a high energy efficiency (η) of 88.2% under an applied electric field of 1000 kV/cm and at 1 kHz frequency was obtained in 300-nm-thick epitaxial PLZT thin films. These high values are due to the slim and asymmetric hysteresis loop when compared to the values in the reference undoped epitaxial lead zirconate titanate Pb(Zr0.52Ti0.48)O3 ferroelectric thin films (Ureco = 9.2 J/cm3 and η = 56.4%) which have a high remanent polarization and a small shift in the hysteresis loop, under the same electric field.

Enhanced energy storage density and its variation tendency in CaZrxTi1−xO3 ceramics

The improved energy storage density and its variation tendency have been investigated for CaZrxTi1−xO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) solid solution ceramics. The dense ceramics with high bulk density above 97% could be obtained, and X-ray diffraction analysis confirms the orthorhombic single phase structure in all compositions. Substitution of Zr4+ obviously increases the sintering temperature, and the homogeneous fine grain structure is obtained. With increasing x, the dielectric constant εr decreases from 175 to 103, while the dielectric strength Eb increases from 435 kV/cm to 756 kV/cm. The highest energy storage density of 2.7 J/cm3 is achieved at x = 0.4, which is much higher than that of CaTiO3 end-member. The energy storage density significantly increases with decreasing the thickness due to the increased dielectric strength (For the samples with x = 0.5, the dielectric strength increases from 584 kV/cm to 756 kV/cm while the energy storage density increases from 1.6 J/cm3 to 2.6 J/cm3 when the thickness changes from 0.50 mm to 0.15 mm).

Enhanced energy storage density and discharge efficiency in the strontium sodium niobate-based glass-ceramics

The niobate-based glass-ceramics with a high energy storage density were prepared by using the controlled crystallization technology in the (Na2O, SrO)Nb2O5SiO2 glass-ceramics. The dielectric properties, energy storage density, and discharge properties were investigated with the variation of the Na/Sr molar ratio. By varying the Na/Sr ratio, the energy storage density raises up to a high value of 10.09 J/cm3. With the variation of the Na/Sr ratio, both dielectric breakdown strength and discharge efficiency have an opposite change trend with the activation energy that reflects the interface polarization of the glass-ceramics. In contrast, for Na/Sr = 1/2, the glass-ceramic has the lower activation energy, which indicates that its interfacial polarization is weaker due to a fine microstructure. Thus, the glass-ceramics for Na/Sr = 1/2 have the characteristics of the higher breakdown strength of 2074 kV/cm and the higher discharge efficiency of 90.1%. Then it may contribute to the high energy storage density capacitor.