Energy Storage Density Research Articles

Enhanced energy storage performance of Bi(Mg0.5Hf0.5)O3 modified K0.5Na0.5NbO3 relaxor ferroelectric ceramics via synergistic strategy

K0.5Na0.5NbO3 (KNN)-based ceramics with large polarization (Pmax) and submicron grain size are considered as promising candidates for dielectric capacitors. However, the existence of significant remnant polarization (Pr) imposes constraints on achieving high recoverable energy storage density (Wrec) and efficiency (η). In this study, we developed and produced ceramic materials by utilizing the composition of (1-x)K0.5Na0.5NbO3-xBi(Mg0.5Hf0.5)O3 ((1-x)KNN-xBMH, x = 0–0.22), employing a viscous polymer rolling technique. We utilized a combined strategy to improve the energy storage capabilities of these materials by manipulating their crystal structures, inducing relaxor behavior, and minimizing microdefects. As a result, we obtained an optimum Wrec of 3.32 J/cm3 and η of 85.37 % at an electric field strength of 350 kV/cm in the x = 0.18 ceramic. Furthermore, excellent temperature stability was observed within the temperature range 20–120 °C, along with frequency stability across frequencies between 5 and 500 Hz. Moreover, at 200 kV/cm in the same composition (i.e., 0.82KNN-0.18BMH), we obtained a power density value as high as 103.13 MW/cm3, accompanied by a fast discharge speed reaching 30.6 ns. Overall, our results demonstrate that the comprehensive energy storage performances exhibited by the 0.82KNN-0.18BMH ceramic make it highly promising for applications in pulsed-power supply.

A microwave-assisted, solvent-free approach for effective grafting of high-permittivity fillers to construct homogeneous polymer-based dielectric film with high energy density

Polymer-based dielectric film capacitors are essential energy storage components in high-power energy storage devices benefiting from their high breakdown strength (Eb) and ultra-fast charge storage/release capability. However, the state-of-the-art commercial capacitor, biaxially oriented polypropylene (BOPP), exhibits limited energy storage density primarily due to low dielectric constant, which hinders the advancement of the film capacitor industry. Introducing high-permittivity (high-k) nanofillers into PP matrix to improve polarization is a promising method but poor filler dispersion leads to a remarkable decrease of Eb, while various strategies to enhance dispersion of fillers typically require sophisticated process involving toxic procedure and consuming significant time and cost. Herein, we show that a novel and scalable surface grafting method for high-k fillers can be achieved by a facile and short-period microwave irradiation with the assistance of silane coupling agent (KH560). As a demonstration, the KH560 is effectively grafted onto the surface of barium titanate (BT), achieving a high grafting ratio of 4.91 % at a yield of 85.1 % within a short time (40s). Furthermore, the surface modified BT nanofillers are introduced into PP matrix and then biaxially stretched. The as-prepared film exhibits excellent dispersion and superior compatibility, resulting in a remarkable enhancement of tensile strength (from 82 MPa to 115.4 MPa), breakdown strength (from 200 MV/m to 254 MV/m), and energy density (from 1.49 J/cm3 to 2.21 J/cm3). This work proposes a new strategy for constructing homogeneous polymer-based dielectric film by microwave activating high-k fillers and is crucial for the design of next-generation energy storage devices.

Study of two thermally integrated pumped thermal electricity storage systems using distinct working fluid groups: Performance comparison

As a competitive new energy storage technology, the thermally integrated pumped thermal electricity storage (TI-PTES) system has received much attention. In this work, two TI-PTES systems are constructed: the RHP-BORC system, which consists of a heat pump cycle (HP) with a regenerator and a basic organic Rankine cycle (BORC), and the RHP-EOFC system, which consists of a HP with a regenerator and an organic flash cycle with ejectors. Meanwhile, R1233zd(E) and Cis-butene are selected to form R1233zd(E)/R1233zd(E) (denoting the working fluid used in the charge and discharge cycles, respectively), R1233zd(E)/Cis-butene, Cis-butene/Cis-butene, and Cis-butene/R1233zd(E) groups. Thermodynamic and economic analyses as well as multi-objective optimization are performed for both systems. The results indicate that for the two systems with different working fluid groups, different parameters have distinct effects on the system performance, and the thermodynamic and economic performance of the RHP-BORC system is better than those of the RHP-EOFC system. For the RHP-BORC system, with the variations of thermal storage temperature, evaporation temperature of heat pump and pinch point temperature difference, the values of different performance metrics of the system with different working fluid groups are close respectively, such as power-to-power efficiency, energy storage density and annual emission reduction. For the RHP-EOFC system under different parameter conditions, when the system uses R1233zd(E)/Cis-butene and Cis-butene/Cis-butene, the performance is better. From the results of the multi-objective optimization, the optimal working fluid group of the RHP-BORC and RHP-EOFC systems are Cis-butene/Cis-butene and R1233zd(E)/Cis-butene, and the values of the power-to-power efficiency and the levelized cost of storage under the optimal solution conditions are 75.76 %, 0.234 $·kWh−1, and 84.31 %, 0.227 $·kWh−1, respectively. The results of the exergy destruction analysis under the optimal solution conditions show that the largest exergy destruction in the RHP-BORC and RHP-EOFC systems are in the condenser (480 kW) and compressor (1275 kW) of the HP cycle. This work expands the configuration of the TI-PTES system, showing promising development prospects. It also provides theoretical support for the further advancement of the TI-PTES system and offers valuable guidance for the design of such systems.

An in-depth comparison of dielectric, ferroelectric, piezoelectric, energy storage, electrocaloric, and piezocatalytic properties of Ba0.92Ca0.08Zr0.09Ti0.91O3 and Ba0.92Ca0.08Sn0.09Ti0.91O3 piezoceramics

The futuristic technology demands materials exhibiting multifunctional properties. Keeping this in mind, an in-depth investigation and comparison of the dielectric, ferroelectric, piezoelectric, energy storage, electrocaloric, and piezocatalytic properties have been carried out on Ba0.92Ca0.08Zr0.09Ti0.91O3 (BCZT) and Ba0.92Ca0.08Sn0.09Ti0.91O3 (BCST) lead-free compounds synthesized through the conventional solid state reaction method. Further, the Rietveld refinement against the XRD patterns affirmed the coexistence of orthorhombic (Amm2) and tetragonal (P4mm) phases at room temperature for both compounds. While BCZT compound demonstrated remarkable dielectric, piezoelectric, and piezocatalytic characteristics with maximum dielectric constant () ≈ 13304 near the Curie temperature ( ≈ 105 °C), converse piezoelectric coefficient ≈ 609 pm V-1 , power density () ≈ 89.71 KW cm-3 at room temperature, and 82.7 % Rhodamine B (RhB) dye degradation capability; on the other hand, BCST compound exceled in superior energy storage density () ≈ 191.8 mJ cm-3 with efficiency η ≈ 73.26% near room temperature and enhanced electrocaloric properties with adiabatic temperature change ≈ 0.980 K, isothermal entropy change ≈ 1.15 J Kg-1K-1 and a higher electrocaloric responsivity ) ≈ 0.49 K mm kV-1. These distinctions arise from the difference in ionic radii, lattice distortion, and the electronic configurations of the dopant ions, leading to a greater polarization change and a lower coercive electric field in the BCST ceramic. The outcome of the present study provides valuable insights for selecting a dopant tailored compound for specific application and underscores the potential of such ceramics in energy storage, piezocatalysis, and the development of advanced solid-state cooling devices for future applications.

The phase composition, dielectric, and energy storage performance of A-site vacancy modulated BaTiO3 ceramics with Bi(In1/2(Li0.5Ta0.5)1/2)O3 modification

The (1-x)Ba0.94Ce0.04TiO3-xBi(In1/2(Li0.5Ta0.5)1/2)O3 (BCT-BILT) relaxor ferroelectric ceramic system was explored based on the A-site vacancy design and defect dipole engineering. The impacts of different doping concentrations on the phase composition, dielectric and energy storage performance of the BCT-BILT ceramics were studied and discussed in detail. The pure BCT and 0.95BCT-0.05BILT samples exhibited a mixed crystal structure of tetragonal (T) and pseudo-cubic (PC) phase, while the BCT-BILT samples with x > 0.05 possessed a cubic (C) phase, accompanied by the secondary phases of BaBi2Ta2O9 and BaTa2O6. With an increase in the BILT doping concentration, the surface morphologies of the ceramics were continuously modulated, and the dielectric loss had been reduced to 0.001 at 1 kHz, which was beneficial to improve the energy storage properties. Compared to the pure BCT, the breakdown field strength was significantly enhanced owing to the formation of Aurivillius phase BaBi2Ta2O9 and the increased dielectric relaxation. Ultimately, the highest energy storage density of Wrec = 0.7 J/cm3 and high energy conversion efficiency of η = 95 % was realized at the composition of x = 0.05 under a small electric field of 130 kV/cm. Furthermore, the good temperature stability with the ΔWrec/Wrec30°C < 9 % and Δη/η30°C < 6.5 % was acquired for the samples with x = 0.20–0.30 in the temperature range of 30–120 °C, owing to the synergistic roles of the defect dipoles, impurities BaBi2Ta2O9, and polar nanoregions (PNRs). The 0.95BCT-0.05BILT ceramic obtains discharge energy density Wdis of 0.35 J/cm3 and fast discharge speed t0.9 of 312 ns at 60 kV/cm, current density CD of 255.4 A/cm2 and power density PD of 10.2 MW/cm3 at 80 kV/cm. This work is of guiding significance for designing and optimizing energy storage performance of lead-free relaxors from the perspective of defect building and engineering.

Superior energy storage properties of BiFeO3 doped NaNbO3 antiferroelectric ceramics

NaNbO3 (NN)-based dielectric ceramics for energy storage have garnered significant interest due to their high saturation polarization, low residual polarization, and superior breakdown strength (Eb). However, the low recoverable energy storage density (Wrec) and efficiency (η) significantly limited their practical application. Herein, BiFeO3 (BF) was incorporated into NN to optimize the energy storage performance. The NN-BF ceramics exhibited pronounced antiferroelectric (AFE) relaxor phase, alongside grain size reduction and Eb enhancement, which contributed to a significant increase of Wrec and η. Specially, the optimum Wrec of 4.43 J/cm³ and η of 71.51 % were achieved at the composition of 0.9NN-0.1BF. Besides, stable energy storage performance was maintained over a wide temperature range (20–120 °C). These results highlight the potential of NN-BF relaxor AFE ceramics as promising candidates for high-performance energy storage applications.

Application of bionic topology to latent heat storage devices

Latent heat storage is employed to address the intermittent supply of renewable energy, and enhancing heat transfer in phase change materials (PCMs) is pivotal for achieving effective heat storage. Currently, the predominant method for improving heat transfer is through the integration of high thermal conductivity fins into heat storage devices. This study introduces an innovative design of a three-tube phase change heat storage device created through bionic topology optimization. The impact of parameters such as penalty factors and filtering radius on the topology structure is analyzed, and the optimal range of fin volume fraction is determined based on energy storage density and energy storage time. Considering the influence of natural convection on heat transfer properties, four distinct heat storage models, including topology-optimized fins, are compared. The heat transfer and flow properties during the processes of melting and solidification, as well as their field synergy, are investigated. The study reveals that the optimized fins exhibit more bionic fractal structures and a larger, more uniform heat transfer contact area. Compared to traditionally optimized fin structures, this research reduces the heat storage time of the three-tube heat storage device by 21.96 % and the heat release time by 38.13 % without compromising the maximum heat storage capacity. The topology-optimized fins demonstrate a fractal dimension similar to natural fractal structures such as branches, leaf veins, antlers, and snowflakes. This study presents a novel bionic structural design approach for high-performance latent heat storage systems.

Excellent energy-storage performance in BNT-BT lead-free ceramics through optimized electromechanical breakdown

Dielectric capacitors with high recoverable energy storage density (Wrec) are in urgent demand for clean energy technologies. However, their lower breakdown strength (Eb) strongly limits their energy storage performance. We, herein, propose a facile method to enhance Eb by enhancing mechanical strength via second phase modulation. The efficiency of this method is validated in the (1-x)(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-xSr(Ta0.5Sb0.5)O3 ((BNT-BT)-xSTS, x = 0.1, 0.15, 0.2, 0.25, and 0.3) ceramics. The introduction of Sr(Ta0.5Sb0.5)O3 (STS) increases the relaxor degree, refines grain size, and most importantly, creates a second phase of BiSb2O7, which hinders dislocation movement and improves mechanical strength. Our results show that the breakdown strength strongly depends on the mechanical strength. The highest hardness of 7.42 GPa accompanied by the largest Eb of 620 kV/cm was obtained in (BNT-BT)-0.25STS sample. The sample exhibits the best energy storage properties of a large Wrec = 8.3 J/cm3, a high efficiency of 82.3 %, and excellent temperature/frequency stability. Furthermore, the sample also exhibits good charge/discharge stability and ultra-fast transient discharge time (62.26 ns). This work provides a theoretical guidance for developing lead-free dielectrics with superior energy-storage performance.

Component design for stabilizing P phase in NaNbO3-based ceramics and the energy storage performance

Antiferroelectric (AFE) ceramic dielectrics are widely recognized for their high potential in high-power pulse equipment applications. Lead-free NaNbO3 (NN) antiferroelectric ceramics have emerged as a prominent research topic in the field of energy storage due to their abundant phase structure, affordability, and moderate bandgap. The metastable ferroelectric Q phase results in a square hysteresis loop for NN at room temperature. However, 0.96NaNbO3-0.04 CaZrO3 (NNCZ) exhibits a typical double hysteresis loop at room temperature with the main crystalline phase being the antiferroelectric P phase, which has poor energy storage performance. In this study, Bi0.5Na0.5TiO3 (BNT) is used to optimize the energy storage performance and stabilize the P phase in NNCZ simultaneously. The dielectric constant and temperature-dependence XRD results that from −100 °C to 350 °C, x = 0.05 undergoes a phase transition from AFE P to AFE R and then to PE S. The solid solution of BNT decreased the sintering temperature of NN-based ceramics and decreased average grain size, thereby facilitating domain size reduction and improving the sample's energy storage efficiency from ∼30 % to ∼60 %, with an effective energy storage density reaching 1.51 J/cm3. The above results demonstrate that enhancing energy storage efficiency can be achieved through component design by reducing average grain size.

Constructing superparaelectric state for NaNbO3-based ceramics electrostatic supercapacitors

A crucial prerequisite for developing high-performance energy storage devices for high pulsed power systems is the urgent necessity to acquire dielectric ceramics with high recoverable energy density (Wrec) and ultrahigh energy efficiency (η), particularly through an environmentally friendly lead-free approach. Here, superparaelectric state with ultra-small nanodomains in NaNbO3-based ceramics is successfully induced by implementing a superparaelectric modulation strategy. This innovation not only reduces the curvature value of the polarization–electric field (P-E) curve, but also produces negligible remanent polarization (Pr) and a linear-like P-E curve, obtaining outstanding efficiency (η) of 92.2 % and high energy storage density (Wrec) of 7.05 J/cm3. This achievement not only opens new avenues for enhancing the energy storage performance of dielectric ceramics but also heralds extensive applications of this material in high-pulse power electronic devices.

Performance analysis and additive screening of a liquid carbon dioxide mixture energy storage system coupled with a coal-fired power plant

Liquid carbon dioxide (CO2) energy storage is a promising technology for balancing grid supply and demand, but liquefaction in high temperature environments is a substantial dilemma. In this study, a novel liquid CO2 mixture energy storage system coupled with a coal-fired power plant is proposed to broaden the liquefiable ambient temperature range, where condensate and feedwater without phase change are used for compression heat recovery and CO2 mixture heating. Firstly, eight refrigerant additives are selected to blend with CO2; then, comparative performance analysis between CO2 mixtures and pure CO2 is conducted, followed by parametric studies; finally, a double-layer decision-making framework based on multi-objective optimization is adopted for additive screening across various ambient temperatures. The results show that a moderate amount of additive favors system safety but degrades thermodynamics and economy, well at high temperatures the performance of CO2 mixture improves and absolutely outperforms pure CO2. CO2/difluoromethane (CO2/R32) reduces the system operating pressure by 20.95 % over pure CO2 at ambient temperature of 298.15 K, accompanied by only 5.78 %, 0.76 % and 9.92 % deterioration in round-trip efficiency, energy storage density and levelized cost of electricity, and exhibits optimal adaptation to varying additive mass fraction. The working fluid unit cost and heat exchangers are the main factors causing these variances. In response to environmental changes, CO2/propylene (CO2/R1270) and CO2/R32 emerge as the two most adaptable mixtures, with the former preferred at low ambient temperatures (288.15–293.15 K) and the latter at high ambient temperatures (298.15–308.15 K). Among all additives, R600 and R161 consistently rank lowest in priority regardless of ambient temperature.

Current insights and future prospects of graphene aerogel-enhanced supercapacitors: A systematic review

Supercapacitors present a compelling alternative to conventional batteries, offering rapid energy storage and high power density. Despite their advantages, they typically fall short in energy density compared to traditional batteries, primarily due to limitations in electrode materials. Graphene Aerogels (GA) have emerged as a promising solution to enhance supercapacitor performance because of their unique properties, such as high surface area and excellent conductivity. This systematic review provides a comprehensive analysis of recent advancements in GA technology, focusing on their synthesis methods and applications in supercapacitors. It highlights significant improvements that GA can bring to Electric Double-Layer Capacitors (EDLCs), pseudocapacitors, and hybrid supercapacitors. Additionally, the review explores GA's potential for enhancing electric generators and integrating into flexible, wearable technologies. Future research directions are emphasised, particularly regarding GA’s potential applications in waste management and environmental protection. The review was conducted through a thorough literature search, prioritising peer-reviewed sources related to GA synthesis and supercapacitor applications. Methodological quality and potential biases of the included studies were assessed using principles similar to the Cochrane Risk of Bias tool. Thematic analysis was employed to synthesise findings and identify key trends and challenges. Limitations such as potential biases and methodological variations are discussed. Overall, this review highlights the technological prospects of GA and provides guidance for future research in supercapacitor development and applications.

Calcium Manganite Based Materials for Thermochemical Energy Storage in High Temperature Solar Thermal Plants: Materials Screening

The urgent need for sustainable energy supply requires maximum exploitation of renewable energy sources. The latter, being of intermittent nature, need to be coupled with efficient energy storage. Solar-thermal power-plants are inherently compatible with thermal storage, which is a cost-efficient method of storing energy for later use but the field is currently dominated by sensible heat molten salts used as heat storage media but with a maximum operating temperature of about 560oC. Certain ceramic materials, able to induce reversible reduction-oxidation reactions under air flow, are promising alternatives to molten salts because they can withstand much higher temperatures (&gt;1000oC) and thus can be integrated with high-efficiency air-Brayton thermodynamic cycles. At the same time the chemical energy stored/released during such reduction-oxidation reactions can boost energy storage density by up to 10 times cf. sensible only concepts. In this framework, Ca-Mn-based perovskite compositions were demonstrated to function effectively as energy storage materials. The current work offers insights on material synthesis parameters to achieve relatively high purity Ca-Mn-based compositions and subsequently optimize their redox performance in the course of a preliminary 5-cycle campaign. Moreover, the occurring structural transitions and their corresponding heat effects are also discussed and elaborated upon. This study is the first step towards the, currently in progress, process of synthesising – at multi kg scale – and shaping these compositions into extruded honeycomb-like monolithic structures for subsequent future application in lab- and pilot-scale high temperature thermochemical energy storage systems.

Superior energy storage performance of Sr0.7Bi0.2TiO3-modified Na0.5Bi0.5TiO3-K0.7La0.1NbO3 lead-free ferroelectric ceramics

Na0.5Bi0.5TiO3 (NBT)-based ceramics exhibit significant potential as energy storage dielectric materials due to their high maximum polarization (Pmax). However, their limited energy storage density significantly restricts their practical applications. To address this, this study optimizes the dielectric energy storage characteristics of lead-free relaxor ferroelectric ceramics based on 0.91Na0.5Bi0.5TiO3-0.09 K0.7La0.1NbO3 (NBT-KLN) by incorporating Sr0.7Bi0.2TiO3 (SBT) relaxor additives. The introduction of SBT helps maintain large polarization and induces local disorderly fields, promoting the formation of polar nanoregions. Subsequently, a viscous polymer processing (VPP) technique was employed to reduce defects and enhance density, markedly improving the breakdown strength (BDS). The findings indicate that the BDS of the optimized 0.30SBT (VPP) ceramics increased to 440 kV/cm, while achieving a high energy storage efficiency (η) of 78 % and an elevated energy storage density (Wrec) of 6.29 J/cm3. Additionally, the 0.30SBT (VPP) ceramics demonstrate excellent temperature stability across a broad temperature range from 30 to 120 °C, making them ideal for long-term operation in variable environments. This study demonstrates superior results compared to previous research, thereby opening up new avenues for developing novel lead-free relaxor ferroelectric ceramics with superior energy storage characteristics.

Modeling of Metal Matrix Concentrated Solar Receivers for sCO2 Power Blocks

Abstract Supercritical CO2 power blocks for Concentrating Solar Power (CSP) with novel metal matrix solar receivers have the potential to reduce operating expenses while improving overall system efficiencies. These concentrated solar receivers integrated with a metal matrix-based phase change (PCM) thermal storage medium provide the compounding effect of an efficient heat exchanger while also integrating thermal storage within the receiver. Detailed numerical modeling of such devices with enthalpy-porosity-based formulation for phase change and turbulent convective heat transfer for the sCO2 microchannels is described in the current work. With sCO2 power blocks operating at temperatures and pressures beyond 800°C and 200 bar, different high-temperature PCMs are studied. A detailed steady charging followed by discharge and charging transients is simulated to analyze the thermal performance of these devices. In the current work, the energy storage density of PCMs is studied, followed by an analysis of the movement of the melt-pool interface over the streamwise length of a high corrugation wavy microchannel. A scaling analysis is carried out to estimate the heat transfer coefficients while compare them with the numerical model predictions. The results from the current work can be utilized for sizing and detailed design of integrated solar receivers for high-temperature sCO2 power block applications.

Exploring the Diversity and Dehydration Performance of New Mixed Tutton Salts (K2V1−xM’x(SO4)2(H2O)6, Where M’ = Co, Ni, Cu, and Zn) as Thermochemical Heat Storage Materials

Tutton salts form an isomorphic crystallographic family that has been intensively investigated in recent decades due to their attractive thermal and optical properties. In this work, we report four mixed Tutton crystals (obtained by the slow solvent evaporation method) with novel chemical compositions based on K2V1−xM’x(SO4)2(H2O)6, where M’ represents Co, Ni, Cu, and Zn, aiming at thermochemical energy storage applications. Their structural and thermal properties were correlated with theoretical studies. The crystal structures were solved by powder X-ray diffraction using the Rietveld method with similar compounds. All of the samples crystallized in monoclinic symmetry with the P21/a-space group. A detailed study of the intermolecular interactions based on Hirshfeld surfaces and 2D fingerprint mappings showed that the main interactions arise from hydrogen bonds (H∙∙∙O/O∙∙∙H) and dipole–ion (K∙∙∙O/O∙∙∙K). On the other hand, free space percentages in the unit cells determined by electron density isosurfaces presented low values ranging from 0.53 (V–Ni) to 0.81% (V–Cu). The thermochemical findings from thermogravimetry, a differential thermal analysis, and differential scanning calorimetry indicate that K2V0.47Ni0.53(SO4)2(H2O)6 salt is the most promising among mixed salts (K2V1−xM’x(SO4)2(H2O)6) for heat storage potential, achieving a low dehydration temperature (≈85 °C), high dehydration enthalpy (≈360 kJ/mol), and high energy storage density (≈1.84 GJ/m3).

A novel offshore energy station with poly-generation of power, fresh water, heat, cold and ice

Energy storage system with large capacity, high efficiency, low cost and long time is major bottleneck, limiting the large-scale deployments of offshore wind power. To improve energy recovery efficiency and energy storage density, here underwater compressed air energy storage (CAES) with isobaric operation is proposed. At about 5 MPa storage pressure, energy recovery efficiency and energy storage density for traditional CAES are respectively 59.45 % and 2.94 kWh/m3, while they increase to 70.35 % and 6.59 kWh/m3 respectively for underwater CAES. The frictional pressure loss of underwater pipeline for air delivery has a remarkable effect on the performance of underwater CAES, and energy recovery efficiency and energy storage density increase from 51.92 % to 67.97 % and from 4.85 kWh/m3 to 6.28 kWh/m3 respectively when the pipeline diameter increases from 0.35 m to 0.45 m. To improve economic profit and utilize interstage compression heat and high frequency electrical energy more efficiently, an offshore energy station with poly-generation is proposed, which has the energy recovery efficiency of 58.26 % and energy storage density of 7.16 kWh/m3, and generates 358.22 MWh of electrical energy, 252.75 GJ of thermal energy, 66.10 GJ of cold energy, 123.23 tons of ice and 257.25 tons of fresh water each day, opening new ways of deploying offshore wind power and offshore energy storage and also providing strong support for developing and utilizing sea resources and conquering the oceans.

Enhanced energy storage density and efficiency of nanocomposite dielectrics by modifying polymer matrix and aminated boron nitride nanosheet

Polymers and fillers with high dielectric constant (εr), charge-discharge efficiency (η) and breakdown strength (Eb) are fundamental to the development of nanocomposite dielectrics for superior energy storage capabilities. Herein, high-εr P(VDF-TrFE) is used to prepare the P(VDF-TrFE)-g-PMMA matrix with elevated εr and η, then the P(VDF-TrFE)-g-PMMA/BNNS-NH2 nanocomposites with uniformly oriented distribution of h-BN is obtained by a squeegee casting process using amino-boron nitride (BNNS-NH2) as fillers. Thanks to the limiting effect of PMMA and the high insulating effect of BNNS-NH2, the energy storage density (Ue) of the nanocomposite is up to 15.1 J/cm3 at 500 MV/m, which is 358 % and 182 % of the original P(VDF-TrFE). Furthermore, the η could reach to 72 %, being 184 % of neat polymer. These results demonstrate that the coordinated enhancement of Ue and η is critical for high performance energy storage, which provide scientific and technological support for the practicability of PVDF-based dielectrics.

Local defect structure design enhanced energy storage performance in lead-free antiferroelectric ceramics

Antiferroelectrics (AFEs) are ideal candidates in dielectric, electromechanical, and electrothermal applications. NaNbO3 (NN), as a lead-free antiferroelectric (AFE) material under extensive investigation, exhibits ferroelectric (FE)-like polarization–electric field (P-E) hysteresis loops, characterized by high remnant polarization and large hysteresis. Herein, the local defect structure design is proposed to achieve high energy storage (ES) density in NN-based AFE ceramics. The pinning effect of defect dipoles and the enhancement of local structural disorder stabilize the AFE phase and reduce hysteresis losses. Consequently, an excellent ES performance of large recoverable energy density (Wrec) of 9.70 J/cm3 and high efficiency (η) of 88.75 % is concurrently obtained in NN-based relaxor AFE ceramics, with outstanding charge–discharge performance (PD∼413.2 MW/cm3, WD∼4.47 J/cm3), which are significantly improved compared to other reported values in lead-free ES ceramics. This indicates that NN-based ceramics are candidates for advanced ES capacitors and provides a feasible modulation approach for the development of new lead-free high-performance dielectric materials.

Molecular dynamics simulation on the variations in characteristics of aqueous solution with diverse additives: Inspirations for binary ice preparation

Ice slurry, as a novel energy storage medium, possesses the superiority of high energy storage density. The freezing point inhibitors are employed to regulate the supercooling phenomenon of water, while the macroscopic experiments are complicated to elucidate the action mechanism. Consequently, this paper adopts molecular dynamic simulation method to investigate the mean square displacement, radial distribution function, hydrogen bonds types, hydrogen bonds number and length of water at various concentrations of ethanol, NaCl, and SiO2 additives. The results indicate that the average number of hydrogen bonds of the system composed with 600 pure water molecules is 1127.24, and the average length of hydrogen bonds is 2.33 Å. Moreover, the addition of alcoholics and chlorides inhibits the hydrogen bonds between water and water molecules, and promotes the generation of hydrogen bonds, thus weakening the diffusion motion of water molecules. Whereas, it is observed that the addition of nanoparticles leads to agglomeration in pure water system, resulting an increase in the viscosity and a decrease in the diffusion rate of the system. The proposed microscopic model can effectively depict the potential interaction mechanisms of additives and water, which is contributing to develop effective freezing point inhibitors and improve the energy utilization efficiency.