High-energy Capacitors Research Articles

Linear dielectric ceramics for near-zero loss high-capacitance energy storage

High energy-density (Wrec) dielectric capacitors have gained a focal point in the field of power electronic systems. In this study, high energy storage density materials with near-zero loss were obtained by constructing different types of defect dipoles in linear dielectric ceramics. Mg2+and Nb5+ are strategically chosen as acceptor/donor ions, effectively replacing Ti4+ within Ca0.5Sr0.5TiO3-based ceramics. The results indicate that under an applied electric field, specific defects such as [MgTi″−VO··] and [NbTi·−Ti3+], can effectively regulate VO·· and electron movement, significantly reducing losses. Furthermore, high-density insulating grain boundaries, reduced VO·· concentrations and diminished carrier mobility contribute to enhanced resistivity, resulting in high Wrec ∼7.62 J/cm3 and η ∼92 % at 640 kV/cm, making it one of the most promising linear dielectrics to date. Notably, Wrec and η remain remarkably stable across a broad range of frequencies (1–500 Hz), temperatures (25–175 °C) and numerous cycles (up to 106). Additionally, finite element software was used to simulate the distribution of dielectric constant, electric potential, and local electric field, further verifying the correlation between microstructure and breakdown resistance. This innovative work provides a sustainable strategy to optimize the energy storage capacity of lead-free ceramics over a wide temperature range through strategic manipulation of defects.

Comprehensive analysis of polyethylene glycol – lauric acid as a promising phase change material: Spectroscopic, thermal, and quantum insights

The increasing need for effective and environmentally sustainable energy storage technologies has delineated phase change materials (PCMs) as prospective candidates for thermal energy storage applications. In this study, we thoroughly analyzed polyethylene glycol (PEG 400) and lauric acid (LA) as promising PCMs by applying spectroscopic study, thermal, and quantum approaches. The thermal stability and chemical compatibility of PEG – LA were investigated using FTIR and Raman spectroscopy, revealing that optimal molecular interactions and structural changes occur at temperatures ranging from −10 °C to 30 °C, especially at higher LA volume fraction (VLA ≥ 60 %), as evidenced by marked blue shifts in the Raman spectra. TGA demonstrated the 2-step degradation of the PEG – LA (6:4), representing good material stability and high thermal conductivity enhancement of 32.24 % due to synergistic interactions among PEG and LA. DSC analysis established a high capacitive energy storage of 181.5 J/g and a phase transition of solid–liquid at room temperature (30–40 °C), which better crystallization properties based on higher LHR and supercooling degree compared with pristine LA. The thermal cycling reliability and FTIR spectra demonstrated the thermal and chemical stability of PEG – LA even after 1000 cycles. Quantum DFT analysis verified the experimental results, exhibiting robust hydrogen bonding interactions that contribute to the thermal stability, phase transition processes, higher energy storage capacity, and reactivity of PEG – LA. These results highlight PEG – LA as a promising and effective PCM for various thermal energy storage applications.

Roll‐to‐Roll Production of High‐Performance All‐Organic Polymer Nanocomposites for High‐Temperature Capacitive Energy Storage

AbstractDielectric materials with significant performance in high temperatures are highly desired, especially in harsh environments. However, the polymer‐based dielectric films have developed so far, the production scale remains at the state of the lab. Here, an all‐organic strategy is proposed by introducing phenyl‐acid‐based polymer nanodots (PAPD) into Polyetherimide (PEI), achieving high capacitive energy storage properties even at 200 °C and mass production by an industrial continuous roll‐to‐roll process. The abundant hydrogen bonding between PAPD and PEI chains ensures uniform distribution for the enhanced interaction between nanofillers and polymer matrix. Under UV irradiation, the electron‐affinity and band gap of the film are further extended, which impede charge transfer and reduction of conductive loss. A low loading (0.3 wt.%) of PAPD renders the membrane significant improvement in breakdown strength and charge–discharge efficiency. An ultrahigh energy storage density of 5.1 J cm−3 with a charge–discharge efficiency of over 90% and charge–discharge cycle stability up to 2 × 104 cycles at 150 °C is observed. Furthermore, a 1000 m long roll of polymeric film is roll‐to‐roll fabricated on an industrial solution‐casting production line and the low cost makes practical commercial scale application possible. Considering the low loading and low cost of nanofiller, this all‐organic design strategy sheds light on the industrial application of high‐temperature dielectric materials.

Surface Modification of AM60 Mg-Al Alloy with Vanadium and V2O5 Sputtered Deposits: Activity in Marine Ambience

Vanadium (~450 nm) and V2O5 (~350 nm) were deposited by DC magnetron sputtering on an AM60 substrate to improve its degradation resistance in marine ambience. According to Raman and XPS analysis, the vanadium nanofilm mainly consists of amorphous V2O3, while V2O5 comprises two sheets of VO5 and VO4 units. After 30 days of immersion of the coated AM60 in a marine model solution (SME), the shift of the pH of the SME to more alkaline values was less pronounced for V2O5-AM60 because of the HCl acid formation during the partial dissolution of V2O5 in the presence of NaCl, and thus, a higher concentration of Mg2+ ions ~100 mg L-1 was released from the Mg (AM60) matrix. The lower concentration of ~40 mg L-1 from the V-AM60 surface was attributed to the possible intercalation of the released Mg ions (cations) into the conductive tunnels of V2O3 as the main component of the vanadium sputtered deposit. This oxide has been reported as a material for high-capacitive energy storage. In this way, the V-deposit provided longer partial protection for the AM60 surface (Mg matrix) from localized pitting attacks.

Balancing Polarization and Breakdown for High Capacitive Energy Storage by Microstructure Design.

The compromise of contradictive parameters, polarization, and breakdown strength, is necessary to achieve a high energy storage performance. The two can be tuned, regardless of material types, by controlling microstructures: amorphous states possess higher breakdown strength, while crystalline states have larger polarization. However, how to achieve a balance of amorphous and crystalline phases requires systematic and quantitative investigations. Herein, the trade-off between polarization and breakdown field is comprehensively evaluated with the evolution of microstructure, i.e., grain size and crystallinity, by phase-field simulations. The results indicate small grain size (≈10-35nm) with moderate crystallinity (≈60-80%) is more beneficial to maintain relatively high polarization and breakdown field simultaneously, consequently contributing to a high overall energy storage performance. Experimentally, therefore an ultrahigh energy density of 131 J cm-3 is achieved with a high efficiency of 81.6% in the microcrystal-amorphous dual-phase Bi3NdTi4O12 films. This work provides a guidance to substantially enhance dielectric energy storage by a simple and effective microstructure design.

Heterostructured n-ZnO@p-CuO nanosheets filled in a polymer matrix for enhanced electrostatic energy storage performance.

Metallized film capacitors use plastic films as the dielectric spacer, and these polymer films generally have low dielectric constants. To boost the electrostatic energy storage density of a film capacitor, advanced high-k films with high electrical breakdown strength and low dielectric loss are highly desired. Herein, polymer nanocomposite films were made by filling ZnO@CuO nanosheets into poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)]. The n-type ZnO nanosheets are synthesized in an aqueous solution. Through a calcination process, thin layers of p-type CuO are coated over the ZnO nanosheets. Compared to pure P(VDF-HFP) and ZnO/P(VDF-HFP) films, the ZnO@CuO/P(VDF-HFP) films exhibit higher dielectric constant and higher breakdown strength. The optimal content of ZnO@CuO nanosheet in the polymer matrix is determined to be 3 wt%, which leads to a dielectric constant of 15.6 at 1 kHz and the highest energy density of 5.6 J cm-3. The efficacy of ZnO@CuO nanosheets in enhancing the dielectric performance of the polymer nanocomposite is elucidated in detail. This research provides a scalable and low-cost strategy to produce polymer nanocomposite films with high capacitive energy storage performance.

Enhanced electrochemical performance of Ce-MOF/h-CeO2 composites for high-capacitance energy storage applications.

The escalating demand for energy storage underscores the significance of supercapacitors as devices with extended lifespans, high energy densities, and rapid charge-discharge capabilities. Ceria (CeO2), known for its exceptional properties and dual oxidation states, emerges as a potent material for supercapacitor electrodes. This study enhances its capacitance by integrating it with Metal-Organic Frameworks (MOFs), carbon-rich compounds noted for their good conductivity. In our research, hollow ceria (h-ceria) is synthesized via hydrothermal methods and amalgamated with Ce-MOF, employing 2,6-dinaphthalene dicarboxylic acid as a ligand, to fabricate Ce-MOF@h-CeO2 composites. The structural and morphological characteristics of the composite are methodically examined using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Fourier-Transform Infrared (FT-IR) spectroscopy. The band gap of the materials is ascertained through UV-Diffuse Reflectance Spectroscopy (UV-DRS). Electrochemical behavior and redox properties of the Ce-MOF composites are explored using Cyclic Voltammetry (CV), Galvanostatic Charge and Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS), providing insights into the material's stability. Electrochemical characterization of the composite reveals maximum specific capacitance, energy density and power density are 2643.78 F g-1 at a scan rate of 10 mV s-1, 249.22 W h kg-1, and 7.9 kW kg-1, respectively. Additionally, the specific capacitance of Ce-MOF synthesized with a 2,6-dinaphthalene dicarboxylic acid (NDC) ligand reaches 995.59 F g-1, surpassing that of Ce-MOF synthesized using a 1,3,5-tricarboxylic acid (H3BTC) ligand. These findings highlight the promising economic potential of high-performance, environmentally sustainable, and cost-effective energy storage devices. The innovative Ce-MOF@h-CeO2 composite materials at the core of this research pave the way for advancing the field of energy storage solutions.

Tunable capacitive charge storage of NiCoLDH@rGO for high-energy capacitor: Performance of flexible solid-state capacitor

The compositionally tunned pristine nickel cobalt layered double hydroxides (NiCoLDHs) and NiCoLDH@reduced graphene-oxide (NiCoLDH@rGO) composites generated via the simple single-pot solvothermal method. The synthesized NiCoLDH and the NiCoLDH@rGO composites were characterized through powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transformed infra-red (FT-IR) spectroscopy, scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDAX), high-resolution transmission electron microscope (HR-TEM), and X-ray photoelectron spectroscopy (XPS) techniques. The XRD, Raman and FT-IR data confirmed the formation of the NiCoLDH with presence of carbonate and nitrate ions in the basal space. Enhanced basal length was observed for the NiCoLDH@rGO composites. The three-electrode system was constructed to analyse the cyclic voltammetry and Galvanostatic charge-discharge studies in 1 M KOH confirmed that the pristine LDHs and the composites are electrochemically active, and the capacity could be tuned by varying (Ni2+/Co3+) mole ratio or the rGO content. The charge storage kinetics in NiCoLDH@rGO was performed through Dunn's approaches and the Power Law, affirmed as the (Ni2+/Co3+) ratio or the rGO content is increased in the composite the capacitive contribution is increased for the charge storage. The NC@RG10 (NiCoLDH with 10 wt% rGO) composite electrode could deliver an enhanced specific capacity of 963C g−1 at a current rate of 1.5 A g−1. Consequently, pristine LDH or composites as positive electrode and rGO as negative electrode was fabricated using the CR-2032 coin-type hybrid capacitor. The laboratory prototype pristine hybrid capacitor (NiCoLDH|1 M KOH|rGO) delivered an enhanced specific energy of 56 Wh kg−1 at specific power of 810 W kg−1, whereas the composite hybrid device (NC@RG10|1 M KOH|rGO) having NC@RG10 electrode delivered an enhanced specific energy of 166 Wh kg−1 at specific power of 638 W kg−1. The NC@RG10 composite-based hybrid device exhibited excellent stability with coulombic efficiency as high as 99 % even at the 10,000th charge−discharge cycle. Reduced aggregation and enhanced conductivity leading to significant capacitive contribution in the NC@RG10 composite is due to the existence of rGO and responsible for the excellent charge storage performance. The fabricated hybrid capacitor powered a red LED on a single charge for 40 min. Fascinatingly, a flexible solid-state hybrid capacitor was also fabricated that delivered an impressive specific energy of 28 Wh kg−1 at a specific power of 553 W kg−1 at a 180° bent angle.

Stepwise-design activated high capacitive energy storage in lead-free NaNbO3-based relaxor antiferroelectric ceramics

Although comparable energy storage performance (ESP) has been realized in NaNbO3 (NN)-based antiferroelectric (AFE) ceramics, how to simultaneously realize large energy density (Wrec), large storage efficiency (η), and outstanding thermal stability still remains a remarkable challenge. Herein, by progressively substituting BiFeO3 (BF) and CaTiO3 (CT), we propose a stepwise-design strategy to activate comprehensive exceptional ESP in NN-based relaxor AFE ceramics. The substitution of BF with high spontaneous polarization and CT with high breakdown strength (Eb) into NN generates stabilized AFE R phase, strong tilt distortions of oxygen octahedron, ultrasmall and highly dynamic polar nanoregions, and refined grains, thus manifesting enhanced high-field polarizability, significantly delayed polarization saturation, and ultrahigh Eb macroscopically. With the deliberate stepwise-design route, we realize an optimal overall ESP in 0.6(0.96NN-0.04BF)-0.4CT relaxor AFE ceramics, featuring a high Wrec of 6.84 J/cm3, a large η of 81.5 %, along with super temperature/frequency/fatigue stabilities, which shows great performance merits compared with previous reports. This work demonstrates that stepwise-design engineering approach by manipulating the crucial structures exerts a positive size effect on the polarization and breakdown response of dielectrics, and can be exploited for designing more high-performance energy storage ceramics.

Excellent energy storage properties in non-stoichiometric Bi0.5Na0.5TiO3-based relaxor ferroelectric ceramics

The rapid development of high-power and pulsed-power techniques inspires extensive investigates on high-performance ceramic-based capacitors. However, the low recoverable energy density (Wrec) hampers their wider applications. Herein, the non-stoichiometric Bi0.5Na0.5TiO3-based ceramics were designed and studied. The proper introduction of oxygen vacancies facilitated activating defect dipole, giving rise to reduced remanent polarization. Consequently, the optimal composition exhibited an exceptional high Wrec of 8.3 J/cm3, a high efficiency of 85%, and excellent anti-fatigue and thermal reliability. This work provides an efficient approach to explore ceramic capacitors with high capacitive energy storage performances.

Local Chemical Clustering Enabled Ultrahigh Capacitive Energy Storage in Pb-Free Relaxors.

Designing Pb-free relaxors with both a high capacitive energy density (Wrec) and high storage efficiency (η) remains a remarkable challenge for cutting-edge pulsed power technologies. Local compositional heterogeneity is crucial for achieving complex polar structure in solid solution relaxors, but its role in optimizing energy storage properties is often overlooked. Here, we report that an exceptionally high Wrec of 15.2 J cm-3 along with an ultrahigh η of 91% can be achieved through designing local chemical clustering in Bi0.5Na0.5TiO3-BaTiO3-based relaxors. A three-dimensional atomistic model derived from neutron/X-ray total scattering combined with reverse Monte Carlo method reveals the presence of subnanometer scale clustering of Bi, Na, and Ba, which host differentiated polar displacements, and confirming the prediction by density functional theory calculations. This leads to a polar state with small polar clusters and strong length and direction fluctuations in unit-cell polar vectors, thus manifesting improved high-field polarizability, steadily reduced hysteresis, and high breakdown strength macroscopically. The favorable polar structure features also result in a unique field-increased η, excellent stability, and superior discharge capacity. Our work demonstrates that the hidden local chemical order exerts a significant impact on the polarization characteristic of relaxors, and can be exploited for accessing superior energy storage performance.

Chemical Design of Pb-Free Relaxors for Giant Capacitive Energy Storage.

Dielectric capacitors have captured substantial attention for advanced electrical and electronic systems. Developing dielectrics with high energy density and high storage efficiency is challenging owing to the high compositional diversity and the lack of general guidelines. Herein, we propose a map that captures the structural distortion (δ) and tolerance factor (t) of perovskites to design Pb-free relaxors with extremely high capacitive energy storage. Our map shows how to select ferroelectric with large δ and paraelectric components to form relaxors with a t value close to 1 and thus obtaining eliminated hysteresis and large polarization under a high electric breakdown. Taking the Bi0.5Na0.5TiO3-based solid solution as an example, we demonstrate that composition-driven predominant order-disorder characteristic of local atomic polar displacements endows the relaxor with a slushlike structure and strong local polar fluctuations at several nanoscale. This leads to a giant recoverable energy density of 13.6 J cm-3, along with an ultrahigh efficiency of 94%, which is far beyond the current performance boundary reported in Pb-free bulk ceramics. Our work provides a solution through rational chemical design for obtaining Pb-free relaxors with outstanding energy-storage properties.

Phosphorous-doped carbon nanotube/reduced graphene oxide aerogel cathode enabled by pseudocapacitance for high energy and power zinc-ion hybrid capacitors

The design and development of energy storage device with high energy/power density has become a research hotspot. Zinc-ion hybrid capacitors (ZHCs) are considered as one of the most promising candidates. However, the application of ZHCs is hindered by their low energy density at high power density due to the unsatisfactory cathode material. In this study, a novel 3D phosphorus-doped carbon nanotube/reduced graphene oxide (P-CNT/rGO) aerogel cathode is synthesized through a synergistic modification strategy of CNT insertion and P doping modification combined with 3D porous design. The as-obtained P-CNT/rGO aerogel cathode manifests significantly increased surface aera, expanded interlayer spacing, and enhanced pseudocapacitance behavior, thus leading to significantly enhanced specific capacitance and superb ions transport performance. The as-assembled ZHC based on P-CNT/rGO cathode delivers a superior energy density of 42.2 Wh/kg at an extreme-high power density of 80 kW/kg and excellent cycle life. In-depth kinetic analyses are undertaken to prove the enhanced pseudocapacitance behavior and exceptional power output capability of ZHCs. Furthermore, the reaction mechanism of physical and chemical adsorption/desorption of electrolyte ions on the P-CNT/rGO cathode is revealed by systematic ex-situ characterizations. This work can provide a valuable reference for developing advanced graphene-based cathode for high energy/power density ZHCs.

A Time of Change

A Time of Change

A novel Sr5BiTi3Nb7O30 tungsten bronze ceramic with high energy density and efficiency for dielectric capacitor applications

Dielectric capacitors with high capacitive energy storage are urgently needed to meet the growing demand for high-performance energy storage devices. Herein, a novel lead-free Sr5BiTi3Nb7O[Formula: see text] (SBTN) tungsten bronze relaxor ferroelectric ceramic is prepared and explored for potential energy storage applications. A high recoverable energy density [Formula: see text] ([Formula: see text] 3.72 J/cm3) and ultrahigh efficiency [Formula: see text] ([Formula: see text] 94.2%) at 380 kV/cm are achieved simultaneously. Both [Formula: see text] and [Formula: see text] exhibit superior stabilities against temperature (30–140[Formula: see text]C), cycles (100 –105) and frequency (1–500 Hz). In addition, a high current density of 796 A/cm2 and a large power density of 71.7 MW/cm3 are achieved, together with good thermal endurance and fatigue resistance. These results demonstrate that the obtained SBTN ceramic can be deemed as the promising candidates for dielectric capacitor applications.

A synergistic two-step optimization design enables high capacitive energy storage in lead-free Sr0.7Bi0.2TiO3-based relaxor ferroelectric ceramics

A two-step design is developed to realize multi-objective synergistic optimizations including high activity/ultrafine PNRs and ultrasmall grain size with compact grain boundaries, showing huge application potential in advanced pulsed power devices.

Study of ferroelectric and piezoelectric response of heat-treated surfactant-based BaTiO3 nanopowder for high energy capacitors

Barium titanate (BaTiO3) nanopowder was synthesized by the alkoxide-hydroxide sol–gel process in an inert (N2) atmosphere. The effect of surfactant sodium dodecyl sulfate (SDS) concentration on the dispersion of BaTiO3 powder was studied at different sintering temperatures, under microwave heating. The phase and structural analysis revealed that the addition of surfactant did not affect the phase transformation of barium titanate. The best outcome was obtained in the case of 0.5 % surfactant-based BaTiO3. At 1100 °C sintering temperature, 0.5 % surfactant-based BaTiO3 exhibited a maximum density of 97.7 %, dielectric constant of 9488, the leading parameters of breakdown strength as 3.12 kV/cm, the figure of merit as 9.98 × 103, and the piezoelectric constant (d33) as 153 pC/N. Moreover, the energy density of 86 kJ/m3 with an energy efficiency of 27.43 % was attained at 1100 °C. For pure BaTiO3 nanopowder, the energy density and the energy efficiency were found as 66.85 kJ/m3 and 50.42 % at 1250 °C, respectively.

Recent Advances in Piezoelectric Materials for Electromechanical Transducer Applications

Ferroelectricity has made a huge impact on science and technology since Joseph Valasek (then a Ph.D. student at the University of Minnesota) discovered it in 1920, a little longer than 100 years ago. Whereas Dr. Valasek’s original research was motivated by the need to develop seismic sensors, at present ferroelectric materials have been extensively studied for applications in high-energy capacitors, energy harvesting systems, night vision sensors, and electrocaloric solid cooling, and, of particular significance, the ferroelectrics are the material-of-choice for numerous electromechanical devices, including underwater acoustic transducers, medical diagnostic and therapeutic transducers, piezoelectric actuators, and ultrasonic motors, to name a few. The progress over the past 100 years has been enormous and it is ongoing: for example, the piezoelectric coefficient d of ferroelectrics has increased from a few pico-Coulomb per Newton to several thousand pico-Coulomb per Newton, which benefits all piezoelectric sensing and actuation devices.

Ag, N and O co-doped carbon cloth as high-capacitance electrodes for high-energy capacitors

Binder-free carbon cloth supported activated carbon electrode has become one of the most promising electrodes in electrochemical capacitors due to its advantages of large specific capacity and long cycle stability, but its application is limited by its inherent low electric double layer capacitance and low electrical conductivity. In this study, a nitrogen-doped carbon layer with Ag particles is formed on the carbon cloth via carbonizing polydopamine layer, which is formed via polymerization reaction, and introducing Ag particles into the obtained carbon layer can improve the electrical conductivity. Subsequently, oxygen-containing functional groups were introduced on the surface of the carbon layer by means of electro-oxidation to provide additional pseudo capacitance to the carbon layer. The obtained electrode exhibits a high area specific capacitance of 2740 mF cm−2 at a current density of 1 mA cm−2, and the capacitance retention rate is 69.1 % when the current density is increased by 15-fold. The symmetric capacitor assembled by this electrode maintains a specific capacity of 87.7 % after 20,000 cycling cycles. The electrode's high specific capacity and long-cycle stability make it as a promising candidate for practical application in energy storage.

High-Energy Electrochemical Capacitors

The decarbonization of energy to meet the low-carbon energy strategy set for 2050 has led to a continuous increase in the contribution of electricity generated from renewables to our growing energy demands, where their inherent intermittency of supply must be addressed by a step-change in energy storage [...]