Excellent Energy Storage Properties Research Articles

Rapid fabrication of binder free nickel cobalt oxide electrodes with dendritic nanostructure for electrochemical energy storage applications

A rapid and facile technique to synthesize nickel cobalt oxide electrodes by photothermal treatment of mixed organometallic precursor solution is reported. Using short and intense pulses of light from a xenon flash lamp, spray coated films are converted into porous nickel cobalt oxide electrodes with dendritic nanostructure. The electrode films fabricated in a few seconds show excellent energy storage properties as supercapacitor electrodes. Specific capacitance of up to 116 Fg−1 and capacitance retention of up to 75 % were observed in samples with low mass loading. Analysis of the cyclic voltammetry (CV) curves shows that capacitance is the dominating charge storage mechanism in these films. To study the effect of varying the mass loading in electrodes, double and triple layered electrodes were also studied. In films with high mass loading, the specific capacitance of the films decreased but areal capacitance continued to increase. A high areal capacitance of up to 243 mFcm−2 is observed in films with high mass loading. CV curve analysis of high mass loading electrodes further shows that in films with higher mass loading, the charge storage mechanism is a mix of capacitance and diffusion processes. The contribution of diffusion increased with increase in the mass loading of the electrodes. This study sheds light into the mechanism of charge storage in electrodes prepared by large-scale-amenable single step process of photonic curing which could be utilized to fabricate electrodes in industrial scale.

Excellent energy storage properties and multi-scale regulation mechanism of Sr(Zr0.5Ti0.5)O3-(Na0.5Bi0.5)0.94Ba0.06TiO3 ceramics

With the rapid advancement of energy storage technologies, dielectric capacitor materials with the outstanding recoverable energy density and power density have garnered significant attention from researchers in the past decades. In this study, (1-x) (Na0.5Bi0.5)0.94Ba0.06TiO3-xSr(Zr0.5Ti0.5)O3 ceramics were prepared via a solid-state reaction method, and the impact of composition on their structure, energy storage performance and stability were investigated. The results revealed that the introduction of Sr(Zr0.5Ti0.5)O3 induced the ferroelectric-relaxor transformation of (Na0.5Bi0.5)0.94Ba0.06TiO3 ceramics, leading to the destruction of the long-range ferroelectric order and the formation of polar nanoregions. In addition, the 0.7(Na0.5Bi0.5)0.94Ba0.06TiO3–0.3Sr(Zr0.5Ti0.5)O3 ceramic exhibited the optimal comprehensive energy storage performance: its recoverable energy storage Wrec attained 8.19 J/cm3 at 650 kV/cm, while the energy storage efficiency η was 85.6 %. Meanwhile, it displayed exceptionally high power density (315.7 MW/cm3) and charge-discharge rate (t0.9 = 50.4 ns). Moreover, this ceramic demonstrated the impressive energy storage performance, in particular, good temperature stability across a wide range of temperatures (20–140 °C), frequency stability (1–200 Hz), and fatigue resistance (1–106 cycles). Finite element analysis showed an enhancement in the breakdown field strength of the ceramics was attributed to the reduction in grain size. First-principles calculations revealed that the band gap increased after adding Sr and Zr elements, and the interactions between the states of O 2p and Ti 3d, Zr 3d, Bi 6p may serve as the microscopic origin of electron energy level polarization and enhanced dielectric performance. Thus, the ceramics have great potential for the application in high-power pulsed electronic systems.

Excellent energy storage properties in ZrO2 toughened Ba0.55Sr0.45TiO3-based relaxor ferroelectric ceramics via multi-scale synergic regulation

Lead-free ceramic capacitors offer ultrahigh power density and ultrafast discharging rates, making them critical energy storage components for advanced pulsed power systems. However, the greatest obstacle to broader applications remains the relatively low energy storage density. In this study, a relaxor ferroelectric ceramic based on (0.6-x)Ba0.55Sr0.45TiO3-0.4Bi0.5Na0.5TiO3-xSrZrO3 ((0.6-x)BST-0.4BNT-xSZ) is prepared using the tape casting method, resulting in an excellent energy density (Wrec ≈ 10.0 J cm−3) and high energy storage efficiency (η ≈ 91 %). The solid solution of linear dielectrics SrZrO3 synergistically regulates both relaxor properties and breakdown strength. The variation of relaxor property was explored utilizing New Glass model and the multi-polarization model, with confirmation provided by piezoresponse force microscopy. Furthermore, the breakdown strength could be attributed to improvements in electric insulation and the widening of the bandgap. As SrZrO3 content increases, the in-situ emergence of the second phase ZrO2, accompanied by a martensitic transformation, not only improves the fracture toughness of ceramics but also serves to elongate the breakdown path. Encouragingly, x = 0.20 ceramics also achieve excellent temperature stability (−95–125 ℃), frequency stability (1–1000 Hz), cycling reliability (1–106 cycles), and great charging-discharging properties. This multiscale synergic regulation strategy plays a guiding role in the screening of high-performance energy storage dielectric materials.

High energy-storage density and giant negative electrocaloric effect in PLZS antiferroelectric thick film ceramics prepared via the tape-casting process

Antiferroelectric materials are highly desired for high energy-storage density capacitors and electrocaloric refrigerator in the future due to their excellent energy storage properties and giant negative electrocaloric effect, which have attracted great attention in recent years. In the present work, a highly recoverable energy density (Wrec) and a large reversible adiabatic temperature change (ΔT) were obtained simultaneously in PLZS thick film ceramics (TFCs). A maximum Wrec of 9.84J·cm-3 with an efficiency of 85.2% at 440kV·cm-1, and a negative ΔT of -9.50 °C at 280kV·cm-1 were obtained. Moreover, the maximum value of electrocaloric strength of 0.98K·m·MV-1 was achieved for Pb0.97La0.02(Zr0.50Sn0.50)O3 TFCs. These results demonstrate that the PLZS TFCs can be applied potentially for high energy-storage density capacitors and refrigerators.

Ultrahigh energy storage performance in AN-based superparaelectric ceramics

Ceramics capacitors, especially featuring antiferroelectric (AFE) structure, are widely used in pulsed power electronic systems due to distinctive high-power density and external field stability. Lead-free AFE material AgNbO3 has seized substantial research attention owing to its unique temperature driven multi-level phase transitions, and many works have greatly improved the energy storage properties by engineering these temperature-dependent phase boundaries. In this work, an ever-unadopted strategy was proposed to modulate the relaxor structure in AgNbO3 by designing room-temperature (RT) superparaelectric phase via Bi incorporation into AN lattice matrix. Structural analysis shows M phase (space group Pbcm) evolves into O phase (space group Cmcm) with 12 mol.% Bi-substitution, breaking the long-range AFE order into polar nanoregions. Hence, an ultra-high recoverable energy density (7.6 J/cm3) and a high efficiency (79 %) are simultaneously achieved in the Ag0.64Bi0.12NbO3 ceramics under 52.2 kV/mm. Moreover, the excellent energy storage properties are accompanied with good temperature and frequency stability, with the variation of Wrec less than ± 15% (over 25–120 °C) and ± 10% (over 1–200 Hz) under 25 kV/mm, respectively. The novel approach reported herein provides a new guidance for designing AgNbO3-based and other AFE materials for high-performance energy storage applications.

Multistage Porous Carbon Derived from Enzyme-Treated Waste Walnut Green Husk and Polyethylene Glycol for Phase Change Energy Storage.

The thermal storage performance, cost, and stability of phase-change materials (PCMs) are critical factors influencing their application in the field of thermal energy storage. Porous carbon, with its excellent support, thermal conductivity, and energy storage properties, is considered one of the most promising support matrix materials. However, the simple and efficient synthesis of high-performance and highly active bio-based materials under mild conditions still faces challenges. In our work, a novel method for preparing new functional composite phase-change materials based on enzyme treatment technology and using waste walnut green husk biomass and polyethylene glycol as raw materials was developed. The enzymatic treatment method exposes the internal structure of the walnut green husk, followed by the adjustment of the calcination temperature to increase the adsorption sites of the biochar, thereby stabilizing polyethylene glycol (PEG). The porous properties of walnut green husk biochar effectively regulate the phase-change behavior of polyethylene glycol. In the biochar carbonized at 600 °C, the PEG loading reached 72.09%, and the absorption heat of the solid-solid phase-change material (SSPCM) reached 194.76 J g-1. This work not only enriches the application of biomass in heat storage but also demonstrates the broad prospects of SSPCMs in solar thermal utilization.

Bi0.5Na0.5TiO3-based energy storage ceramics with excellent comprehensive performance by constructing dynamic nanoscale domains and high intrinsic breakdown strength

Lead-free ceramic-based dielectric capacitors show huge potential in electrical energy storage in pulsed power systems due to their fast charge/discharge rate, ultrahigh power density and environmental friendliness. However, unsatisfied charge/discharge performance characterized by inferior recoverable energy storage density (Wrec generally <5 J/cm3) has become a key bottleneck to restrict their applications in cutting-edge energy storage devices. In this paper, we focus on simultaneously realizing ultrahigh Wrec and efficiency (ƞ) in eco-friendly Bi0.5Na0.5TiO3 (BNT)-based dielectric ceramics via chemical doping. Interestingly, highly dynamic polar nanoregions (PNRs) and nanodomains are constructed by incorporating Sr0.7Nd0.2TiO3 (SNT) into 0.94BNT-0.06BaTiO3. Of great importance, the resulting relaxor ferroelectrics (RFEs) exhibit high bulk resistivity, submicron grain size and wide band gap due to high level of SNT doping accompanying with 1 at% Nb donor doping. Therefore, excellent energy storage properties with ultrahigh Wrec∼8.08 J/cm3 and ƞ∼92.1% are achieved due to coexistence of large polarization difference (ΔP=Pmax−Pr) and giant dielectric breakdown electric field (Eb∼540 kV/cm). Furthermore, excellent temperature/frequency/cycling stability characterized by ΔWrec < ±4% and Δη < ±2% ensure the energy storage applications of the studied dielectric ceramics over an enormous range of scales.

Samarium-modified PLZST-based antiferroelectric energy storage ceramics for low-temperature sintering in reducing atmosphere

The energy storage properties of pure PLZST-based antiferroelectric ceramics are excellent; however, the high sintering temperature renders them unsuitable for co-firing with copper inner electrodes as MLCC dielectric materials. The proven BASK glass additive was employed in this study to lower the sintering temperature of PLSZT ceramics, while simultaneously doping Sm3+ ions to enhance their sintering performance under reducing atmospheres. The precise evaluation process confirmed that the addition of glass effectively reduced the sintering temperature to 1040 °C. Furthermore, the defect association of Sm3+ doping hindered the formation of oxygen vacancies, facilitated ceramic grain growth, and significantly enhanced insulation resistivity. Consequently, an ultrahigh recoverable energy density (Wrec) of 5.19 J/cm3 with a high energy storage efficiency (η) of 94.5% are achieved at an electric field of 430 kV/cm. Moreover, the AFE ceramics possess excellent discharge energy storage properties with a high discharge energy density (Wd) of 4.26 J/cm3 and a large power density (Pd) of 139 MW/cm3.

Excellent energy storage properties in BNT-based relaxor ceramics via composition optimization strategy

In this work, lead-free energy storage ceramics, (1−x)(0.95Bi0.5Na0.5TiO3-0.05Ba0.85Ca0.15Zr0.1Ti0.9O3)-xSr0.7La0.2SnO3 (BNT-BZCT-xSLS, x = 0.05, 0.10, 0.15, and 0.20), were prepared. The crystal structure, microstructure, dielectric properties, ferroelectric properties, energy storage properties, and charge-discharge performance of BNT-BZCT-xSLS were systematically studied. Among the products, BNT-BZCT-0.15SLS exhibited the highest energy storage performances (W = 2.95 J/cm3, W rec = 2.09 J/cm3, and η = 71%) due to its dense microstructure, finer grain size, and improved relaxation. Furthermore, the BNT-BZCT-0.15SLS also showed an ultra-fast charge and discharge speed (t0.9 = 0.033 μs) and a large power density (P D = 28.0 MW/cm3).

Optimized energy storage properties of Bi0.5Na0.5TiO3-based lead-free ceramics by composition regulation

To meet the demand for miniaturization and integration of electronic and electrical equipments, developing dielectric capacitors with excellent energy storage properties is of utmost importance. Bi0.5Na0.5TiO3-based ceramics have been investigated extensively for potential energy storage applications. However, its low breakdown strength Eb and high remnant polarization Pr limit the energy storage density and efficiency (η). Therefore, we explored a synergistic design strategy of domain control and grain size adjustment via La doping to successfully synthesize 0.8Bi0.5Na0.5TiO3-0.2NaNbO3-xLa2O3 (0.8BNT-0.2NN-xLa2O3) ceramics with superior energy storage properties to overcome above issues. It shows that the composition regulation by antiferroelectric NaNbO3 results in improved disrupted long rang order ferroelectric domain structure, effectively promoting the formation of polar nanoregions, subsequently weakening Pr and enhancing relaxation behavior. The introduction of antiferroelectric NaNbO3 effectively improves the η of the system. Moreover, the grain size is decreased and densification is enhanced after La tailoring, which is beneficial for the Eb and recyclable energy storage density (Wrec). Finally, a high Wrec of 4.40 ± 0.20 J/cm3 and η of 80.1 ± 2.1% at 450 kV/cm are obtained in 0.8BNT-0.2NN-0.07La2O3 ceramic. Besides, the sample demonstrates admirable temperature stability (25–175 °C) and frequency stability (10–100 Hz). Simultaneously, it displays stable discharge energy density, rapid discharge time of 0.36 μs, and good fatigue endurance (105 cycles). The results offer useful guidance for the design of novel ceramic capacitors with comprehensive energy storage performance.

High-entropy MXene Ti3(B0.25C0.25N0.25O0.25)2O2 as anode materials for lithium-ion batteries: Insight from first principles

Two-dimensional MXene materials had attracted extensive research interest due to their excellent energy storage properties. Meanwhile, high-entropy materials exhibited excellent properties due to their unique lattice structure and stability. This study investigated the potential of a high-entropy MXene, Ti3(B0.25C0.25N0.25O0.25)2O2, as an advanced anode material for lithium-ion batteries through first-principles calculations. The structural, electronic, and lithium adsorption properties were systematically examined. Notably, the material exhibited a metallic-like character with favorable adsorption energies for lithium ions at the C-site. Additionally, the diffusion energy barrier for Li-ions was found to be exceptionally low at 0.18 eV, indicating promising rate performance. The study explored the adsorption of multiple lithium layers, and the maximum theoretical specific capacity of 466.59 mAh/g and a minimum open circuit voltage of 0.48 V. The stability of the material after lithium adsorption was confirmed through analyses of formation energy and cohesive energy. Overall, this research highlighted the considerable potential of high-entropy MXene as a stable and high-performance anode material for lithium-ion batteries.

Trilayer structured ceramic/polymer nanocomposites with superior breakdown strength and discharged energy density

The excellent dielectric constant (εr) and breakdown strength (Eb) of dielectric nanocomposites are the necessary conditions for their excellent energy storage properties (ESPs) in microelectronics and power systems. In recent years, inorganic nanofillers and multilayer structure design have provided an efficient way to improve the ESPs of dielectric composites. Herein, we selected 0.8Bi0.5(Na0.82K0.18)0.5TiO3-0.2Sr(Sc0.5Nb0.5)O3 cecamic nanoparticles (BNKT-SSN NPs) with high εr and low loss as nanofillers, and prepare novel trilayer structured BNKT-SSN/P(VDF-HFP) nanocomposites to improve the εr and Eb. The investigated phenomena demonstrate that due to the contribution of BNKT-SSN NPs incorporation and interfacial polarization between neighboring layers, the εr and Eb of the trilayer structured BNKT-SSN/P(VDF-HFP) nanocomposites are enhanced while the dielectric loss (tanδ) and leakage current density are suppressed. It is worth noting that the Eb is measured up to 650 MV m−1 when the intermediate layer fillers BNKT-SSN NPs of the trilayer structured nanocomposite is 0.75 vol%, and the discharged energy density (Ud) and energy efficiency (η) are 25.79 J cm−3 and 70.07 %, respectively. In this work, it's demonstrates that the incorporation of inorganic ceramic fillers and the trilayer structured design provide a feasible approach of improving the ESPs of dielectric nanocomposites.

Phase transition characteristics, electrical and optical properties of AgNbO&lt;sub&gt;3 &lt;/sub&gt;crystals grown by flux method

&lt;sec&gt;AgNbO&lt;sub&gt;3&lt;/sub&gt;, with the antiferroelectric ordering and huge polarization (&gt;50 μC/cm&lt;sup&gt;2&lt;/sup&gt;), has potential applications in smart electronic devices, such as energy storage dielectrics, large displacement actuators, and electrocaloric cooling device. Large electro-strain and excellent energy storage properties have been reported in AgNbO&lt;sub&gt;3&lt;/sub&gt;-based ceramics. Nevertheless, the lack of systematic research on the AbNbO&lt;sub&gt;3&lt;/sub&gt; single crystals increases the difficulty in further understanding their structure-property relationship.&lt;/sec&gt;&lt;sec&gt;In this work, &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}${\left\langle {001} \right\rangle _c}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20230984_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20230984_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; oriented AgNbO&lt;sub&gt;3&lt;/sub&gt; single crystals with a large size (maximum size 5 mm×4 mm×4 mm) and high quality are successfully grown by the flux method. The phase transition characteristics are studied by the X-ray diffraction, temperature dependence of dielectric data and AC impedance, polarized light microscope photos, and differential scanning calorimetry curves. The electrical and optical properties are studied by the ferroelectric response and electro-strain response, optical absorbance spectrum and photo-dielectric effect.&lt;/sec&gt;&lt;sec&gt;The AgNbO&lt;sub&gt;3&lt;/sub&gt; single crystals with the &lt;i&gt;M&lt;/i&gt; phase exhibit the same domain structure. When the structure changes from &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt; to &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;3&lt;/sub&gt;, the contrast of the PLM image is darkened. Correspondingly, the conductivity and dielectric loss significantly increase, which relates to the dynamic behaviors of the carriers. Interestingly, neither exothermic peak nor endothermic peak relating to the &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt;-&lt;i&gt;M&lt;/i&gt;&lt;sub&gt;3&lt;/sub&gt; transition is observed. The active energy for the &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;3&lt;/sub&gt; phase AgNbO&lt;sub&gt;3&lt;/sub&gt; single crystal is ~1.24 eV. When the structure changes from orthogonal &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;3&lt;/sub&gt; to paraelectric orthogonal &lt;i&gt;O&lt;/i&gt;, the domain structure disappears and the contrast becomes darker. The finding indicates that the anisotropy of the crystals disappears. At the same time, an obvious thermal hysteresis observed in the DSC curve reveals that the &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;3&lt;/sub&gt;-&lt;i&gt;O&lt;/i&gt; transition is first-order. At room temperature, the direct band gap of AgNbO&lt;sub&gt;3&lt;/sub&gt; single crystal is ~2.73 eV, which is slightly narrower than that of AgNbO&lt;sub&gt;3&lt;/sub&gt; ceramic. Below the critical electric field, AgNbO&lt;sub&gt;3&lt;/sub&gt; single crystal shows an electro-strain of 0.076% under &lt;i&gt;E&lt;/i&gt;&lt;sub&gt;m&lt;/sub&gt; = 130 kV/cm. The obtained electro-strain value is much higher than that of AgNbO&lt;sub&gt;3&lt;/sub&gt; ceramic under the same electric field. The relative permittivity increases from 70 to 73 under the green laser irradiation, showing an apparent photo-dielectric effect. We believe that our study can assist in the further understanding of the phase transition characteristics and physical properties in AgNbO&lt;sub&gt;3&lt;/sub&gt; single crystals.&lt;/sec&gt;

Achieving synergistic improvement in dielectric and energy storage properties at high-temperature of all-organic composites via physical electrostatic effect.

In response to the increasing demand for miniaturization and lightweight equipment, as well as the challenges of application in harsh environments, there is an urgent need to explore the new generation of high-temperature-resistant film capacitors with excellent energy storage properties. In this study, we report an all-organic composite system based on two polymers with similar densities and high glass transition temperatures, achieving a synergistic effect of dielectric constant and breakdown strength. The preparation of the composite is simple, overcoming the challenge of dispersing nanoparticles in traditional organic-inorganic systems. The high polarity of polyethersulfone can modulate the polarization properties of the composites and, through a physical electrostatic effect, inhibit dipole relaxation, further reducing the current density of the composite dielectric at high temperatures, resulting in a significant improvement in insulating properties. The 9 : 1 composite dielectric at 150 °C demonstrates an energy storage density of up to 6.4 J cm-3 and an efficiency of 82.7%. This study offers a promising candidate material and development direction for the next-generation energy storage capacitors with broad application prospects.

Phonon mode and dielectric function dynamics of Bi0.5Na0.5TiO3-xSm2Ti2O7 ceramics during the phase transitions discovered by Raman scattering and spectroscopic ellipsometry

Recently, Bi0.5Na0.5TiO3-based ceramics have drawn widespread attention due to their excellent energy storage properties. Here, a comprehensive analysis of the composition- and temperature-driven transition processes in (1 − x)Bi0.5Na0.5TiO3-xSm2Ti2O7 (BNST-x) polycrystals have been presented using Raman scattering and spectroscopic ellipsometry. With increasing Sm2Ti2O7 content, BNST-x ceramic gradually becomes disordered and belongs to the superparaelectric state at x = 0.12 near room temperature. Moreover, the thermal evolution of the lattice kinetic behaviors shows two crucial temperatures: the depolarization temperature Td and the temperature at the maximum dielectric permittivity Tm, which suggest the transitions from nonergodic relaxor ferroelectric—ergodic relaxor (ER) ferroelectric and ER ferroelectric—superparaelectric, respectively. It is noteworthy that the series of changes is closely related to the ordering degree of the B-site ion affected by the doping and the temperature. This work gives an insight into the connection among the phonon behavior, electronic transition, and lattice structure of BNST-x ceramics, which can further understand the phase transition mechanisms under the doping and thermal field.

Enhancement of energy storage performances in BaTiO3-based ceramics via introducing Bi(Mg2/3Sb1/3)O3

Lead-free relaxor ferroelectric ceramics have attracted extensive attention on account of their excellent energy storage properties. However, these ceramics still have some difficulties in improving the energy storage density, efficiency and stability. Herein, (1-x)BaTiO3-xBi(Mg2/3Sb1/3)O3 (BT-xBMS, x = 0.08, 0.12, 0.16, and 0.20) ceramics were designed in this study. After the addition of Bi/Mg/Sb (BMS) elements into BaTiO3(BT) system, the grain size of ceramics increases obviously. And the grain boundary activation energy increases with the increase of resistivity, which is due to the difficulty of grain boundary oxygen vacancy transition. This measure can effectively enhances the breakdown strength (Eb), thereby improving the energy storage properties. Significantly, it is worth mentioning that BT-0.16BMS ceramics exhibit excellent total energy density (Wtotal = 4.56 J/cm3), large recyclable energy storage density (Wrec = 4.28 J/cm3) and high efficiency (η = 93.70 %) under Eb of 550 kV/cm. In particular, BT-0.16BMS ceramics achieved excellent current density (CD = 1475.58 A/cm2), power density (PD = 177.07 MW/cm3), discharge energy density (Wd = 1.35 J/cm3) and extremely fast discharge time (t0.9 = 27.34 ns). In addition, BT-0.16BMS ceramics have excellent temperature range (20–140 °C) and frequency (1–200 Hz) stability. Therefore, the excellent energy storage properties make BT-0.16BMS ceramics have broad prospects in advanced pulse power capacitors.

Asymmetric supercapacitor based on nano-flower Ni-Co-O/C electrodes

Ni-Co-O material is the most representative polymetallic compound and has exhibited excellent energy storage properties. However, the high cost of composite restricts the practical application of Ni-Co-O material. In this paper, a simple and low-cost method is used to grow Ni-Co-O/C nanoarrays directly on a conductive matrix. The results show that the three-dimensional nanoflower-like Ni-Co-O/C composite has better electrochemical performance than that of the nanosheet Co-O/C binary composite. This microstructure provides a shorter path for electron transport, making the material high electron transport efficiency. The specific capacitance of Ni-Co-O/C/AC asymmetric supercapacitor can reach 128.75 mF cm−2 at 2 mA cm−2. Under the condition of 20 mA cm−2, after 4000 cycles of charge and discharge, the capacitance retention rate is maintained at 99.8 %. This 3D flower-like structure not only helps provide an open framework and rapid ion diffusion, but also exposes more active sites and enhances charge storage performance. Ni-Co-O/C calcined in nitrogen shows more abundant defect structure and larger specific surface area, which is further conducive to Ni-Co-O/C electrodes to expose more active sites and enhance the rapid diffusion and reaction of electrolyte ions.

Rational Design of High-Performance Electrodes Based on Ferric Oxide Nanosheets Deposited on Reduced Graphene Oxide for Advanced Hybrid Supercapacitors.

The core strategy for constructing ultra-high-performance hybrid supercapacitors is the design of reasonable and effective electrode materials. Herein, a facile solvothermal-calcination strategy is developed to deposit the phosphate-functionalized Fe2O3 (P-Fe2O3) nanosheets on the reduced graphene oxide (rGO) framework. Benefiting from the superior conductivity of rGO and the high conductivity and fast charge storage dynamics of phosphate ions, the synthesized P-Fe2O3/rGO anode exhibits remarkable electrochemical performance with a high capacitance of 586.6Fg-1 at 1Ag-1 and only 4.0% capacitance loss within 10000 cycles. In addition, the FeMoO4/Fe2O3/rGO nanosheets are fabricated by utilizing Fe2O3/rGO as the precursor. The introduction of molybdates successfully constructs open ion channels between rGO layers and provides abundant active sites, enabling the excellent electrochemical features of FeMoO4/Fe2O3/rGO cathode with a splendid capacity of 475.4C g-1 at 1Ag-1. By matching P-Fe2O3/rGO with FeMoO4/Fe2O3/rGO, the constructed hybrid supercapacitor presents an admirable energy density of 82.0Whkg-1 and an extremely long working life of 95.0% after 20000 cycles. Furthermore, the continuous operation of the red light-emitting diode for up to 30min demonstrates the excellent energy storage properties of FeMoO4/Fe2O3/rGO//P-Fe2O3/rGO, which provides multiple possibilities for the follow-up energy storage applications of the iron-based composites.

Excellent energy storage properties with ultrahigh Wrec in lead-free relaxor ferroelectrics of ternary Bi0.5Na0.5TiO3-SrTiO3-Bi0.5Li0.5TiO3 via multiple synergistic optimization

Advanced energy storage capacitors play important roles in modern power systems and electronic devices. Next-generation high/pulsed power capacitors will rely heavily on eco-friendly dielectric ceramics with high energy storage density (Wrec), high efficiency (η), wide work temperature range and stable charge-discharge ability, etc. Lead-free Bi0.5Na0.5TiO3 (BNT) based relaxor ferroelectric (RFE) ceramics are considered as one of the most promising candidates for energy storage capacitors. However, the application fields of them are greatly limited by their relatively low Wrec (generally <5 J/cm3). In this paper, excellent energy storage properties characterized by a great breakthrough in Wrec are achieved in a novel BNT system, (1-x)BNT-x(0.7SrTiO3-0.3Bi0.5Li0.5TiO3)+0.5 at.%Nb2O5 (x = 0, 0.1, 0.2, 0.3, 0.4), by synergistically constructing highly dynamic polar nanoregions (PNRs) and nanodomains, ultrafine grains (submicron size) and intrinsic conduction. Of great importance, the x = 0.4 ceramic exhibits an ultrahigh Wrec of 8.63 J/cm3 as well as a high efficiency (ƞ) of 89.6 % under a giant electric field of 520 kV/cm, due to coexistence of ultrahigh polarization difference (ΔP=Pmax −Pr) and high dielectric breakdown electric strength (Eb). Furthermore, excellent temperature stability (20−180 °C), frequency stability (1 − 500 Hz), and cycling stability (1 − 105 times) with the variation of Wrec < ±4 % and η < ±3 % are also found in the x = 0.4 ceramic. These results demonstrate that it is a very promising lead-free dielectric capacitor with enormous energy storage applications.

Modulating polarization and carrier migration characteristics via constructing sandwich-structured heterojunction interfaces for achieving excellent high-temperature energy storage properties in polymer nanocomposites

Dielectric polymer nanocomposites are ideal choices for electrostatic energy storage due to their high power density and reliability, but they cannot operate efficiently at high temperature. To solve this issue, herein, we designed and developed sandwich-structured montmorillonite (MMT)/polyetherimide (PEI)-(Pb,La)(Zr,Sn,Ti)O3 (PLZST) antiferroelectrics (AFEs)@dopamine (DA)-MMT/PEI nanocomposites. On one hand, compared to current wide-band gap fillers, i.e., TiO2, Al2O3, ZrO2, and MgO, two-dimensional MMT nanosheets possess unique electrically insulating performances along the thickness direction, and thus can effectively stop charges injecting and migrating, causing low conduction loss, and large breakdown strength (Eb). On the other hand, PLZST AFEs with orthorhombic structure can exhibit high maximum electric displacement (Dmax) and small remnant electric displacement (Dr) at high temperature, which is beneficial for achieving large Dmax-Dr in the nanocomposites. In addition, large dielectric constant differences between MMT/PEI and PLZST@DA/PEI layers can inhibit electrical tree growth, resulting in further raised Eb. Finite element simulations on electrical tree evolving confirm experimental breakdown results. The sandwich-structured nanocomposite displays impressive high-temperature (150 °C) capacitive performances possessing meanwhile a high Eb of 5265.9 kV/cm, large discharged energy density (Ue) of 7.1 J/cm3, being about 6 times that of the commercial biaxially oriented polypropylene, and large charge-discharge efficiency (η) of 81.6 %, which exceeds obviously latest polymer and polymer composites in terms of overall energy storage performances. More encouragingly, it displays an ultrahigh power density of 15.63 MW/cm3 and ultrafast discharge rate of 19.2 ns at 150 °C, indicate its excellent application potential in high-temperature pulse power systems.