A hybrid supercapacitor assembled with CoZnNiS/CNTs/rGO nanoarrays and carbon spheres/rGO achieves an ultra-high volumetric/gravimetric energy density of 65.2 Wh L−1/60.4 Wh kg−1 at a power density ...of 1308 W L−1/1200 W kg−1.
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•CNTs/rGO supported MOFs derived CoZnNiS nanoarrays are successfully prepared.•CoZnNiS@CNTs/rGO film endows the electrode with ultrahigh volumetric mass density of 1.28 g cm−3.•The binder-free electrode displays a high volumetric capacity of 1727.0 F cm−3.•The hybrid supercapacitor achieves an ultra-high volumetric energy density of 65.2 Wh L−1.
With the increasing demand for miniaturization and portable energy storage system, it is an urgent necessary that developing high volumetric energy density supercapacitors with small volumes. Herein, an integrated self-supporting CoZnNiS@CNTs/rGO composite film electrode with the thickness of about 6 μm was designed. In the unique structure, porous CNTs/rGO film is served as conductive substrate to support the CoZn-MOFs derived vertically oriented two-dimensional CoZnNiS nanoarrays. The self-supporting film endows the electrode a high volumetric mass density of 1.28 g cm−3 and superior electron-ion transport channel, which displays a maximum specific capacitance of 1349.2 F g−1 as well as high volumetric capacity of 1727.0 F cm−3 at 1 A g−1. Besides, a porous film of pure carbon materials (carbon spheres integrated graphene) was designed and used as the negative electrode in supercapacitor. When assembled a hybrid supercapacitor based on the above two self-supporting electrodes, the device delivers up an ultra-high volumetric/gravimetric energy density of 65.2 W h L−1 (60.4 W h kg−1) at a power density of 1308 W L−1 (1200 W kg−1). Moreover, the asymmetric supercapacitor also displays an ultra-long lifetime with 90.6% retention after 10,000 cycles. These outstanding performances make the CoZnNiS@CNTs/rGO electrode could be a promising candidate for next-generation high volumetric/gravimetric energy density supercapacitors, especially in the limited space.
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•A new theory named “crossover relaxor ferroelectrics” were reported.•Crossover relaxor 0.9BBNT-0.1SSN ceramic processes high Wrec of 2.02 J/cm3 and η of 90.18% at ...206 kV/cm.•0.9BBNT-0.1SSN ceramic exhibits strong chemical and electrical uniformity.•The excellent thermal stability, frequency stability, and cycle life stability have been achieved in 0.9BBNT-0.1SSN ceramic.
With a view to the rapid development of pulsed power capacitors, the demands for higher energy density, energy efficiency, and stability have increased significantly. A large amount of research has been devoted to the energy storage field of dielectric ceramics, however, scientific and effective strategy to design novel materials with excellent energy storage performance is still lacking. In this work, a new guideline was proposed that higher energy density and efficiency are easier obtained in crossover relaxor ferroelectrics, which is between normal ferroelectrics and relaxor ferroelectrics. Based on this theory, a series of lead-free (1-x)(0.65BaTiO3-0.35Bi0.5Na0.5TiO3)-xSr(Sc0.5Nb0.5)O3 ((1-x)BBNT-xSSN, x = 0, 0.05, 0.10, 0.15, 0.20) ceramics are designed and investigated. Optimal energy storage properties are achieved in 0.9BBNT-0.1SSN ceramic, with a large Wrec of 2.02 J/cm3 and a high η of 90.18% under a moderate electric field of 206 kV/cm. More importantly, both the Wrec and η of 0.9BBNT-0.1SSN ceramic show outstanding stability (including frequency, thermal, and cycle life stability) at 150 kV/cm, which is superior to other lead-free ceramics. These results demonstrate 0.9BBNT-0.1SSN ceramic is a promising candidate for practical energy storage applications.
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•BMN modified BCZT exhibits higher polarization and breakdown strength.•0.925BCZT-0.025BMN ceramic possesses a high energy density and efficiency.•Excellent temperature and frequency ...stability of energy density have been achieved.•Domain engineering on the nanoscale was designed and observed in the ceramics.
The improvement of energy density and efficiency is currently the main challenge in the application of lead-free dielectric energy-storage materials. Relaxor ferroelectric ceramics are the most commonly selected materials for pulsed power capacitors because of their inherent advantages, such as ultra-high power density, fast charging/discharging, and long lifetime. In this study, BiMg2/3Nb1/3O3 (BMN) was doped to enhance energy density and efficiency in the (1−x)Ba0.85Ca0.15Zr0.1Ti0.9O3-xBiMg2/3Nb1/3O3 systems based on the adjusted breakdown strength and polarization. As a result, a giant recoverable energy density of 3.81 J/cm3 and a high energy efficiency of 90.5% were simultaneously achieved in the 0.925BCZT-0.075BMN ceramic, which the energy density is 26 times as large as that of BCZT ceramic. Excellent temperature (−25 to 100 °C) and frequency (1–100 Hz) stability of recoverable energy density and energy efficiency were confirmed with the fluctuations below 4.5%. Domain engineering on the nanoscale was designed in relaxor ferroelectrics, which effectively improved the energy storage performance. Our study provides a feasible guideline to develop lead-free ceramics for electrical energy storage applications.
We have investigated a series of compositions in the pseudo-ternary lead-free alloy system Na1/2Bi1/2TiO3-BaTiO3-BiFeO3 with regard to its energy storage density and discharge efficiency. A ...composition 0.4(Na0.5Bi0.5TiO3)-0.225BaTiO3-0.375BiFeO3 of this series was identified to give the best energy density and discharge efficiency. While conventional sintering gave energy density of 0.77J/cm3 and discharge efficiency of 67%, we achieved a remarkable increase in energy storage density (∼1.4J/cm3) and discharge efficiency (∼90%) by using spark plasma sintering of this composition. Our results suggest that this alloy system can be a potential lead-free candidate for high electric energy storage and discharge efficiency.
To investigate the energy evolution characteristics of rock materials under uniaxial compression, the single-cyclic loading–unloading uniaxial compression tests of four rock materials (Qingshan ...granite, Yellow sandstone, Longdong limestone and Black sandstone) were conducted under five unloading stress levels. The stress–strain curves and failure characteristics of rock specimens under the single-cyclic loading–unloading uniaxial compression tests basically corresponded with those of under uniaxial compression, which indicates that single-cyclic loading–unloading has minimal effects on the variations in the loading–deformation response of rocks. The input energy density, elastic energy density and dissipated energy density of four rocks under five unloading stress levels were calculated using the graphical integration method, and variation characteristics of those three energy density parameters with different unloading stress levels were explored. The results show that all three energy density parameters above increased nonlinearly with increasing unloading stress level as quadratic polynomial functions. Meanwhile, both the elastic and dissipated energy density increased linearly when the input energy density increased, and the linear energy storage and dissipation laws for rock materials were observed. Furthermore, a linear relationship between the dissipated and elastic energy density was also proposed. Using the linear energy storage or dissipation law, the elastic and dissipated energy density at any stress levels can be calculated, and the internal elastic (or dissipated) energy density at peak compressive strength (the peak elastic and dissipated energy density for short) can be obtained. The ratio of the elastic energy density to dissipated energy density with increasing input energy density was investigated using a new method, and the results show that this ratio tends to be constant at the peak compressive strength of rock specimens.
In this work, a high‐voltage output and long‐lifespan zinc/vanadium oxide bronze battery using a Co0.247V2O5⋅0.944H2O nanobelt is developed. The high crystal architecture could enable fast and ...reversible Zn2+ intercalation/deintercalation at highly operational voltages. The developed battery exhibits a high voltage of 1.7 V and delivers a high capacity of 432 mAh g−1 at 0.1 A g−1. The capacity at voltages above 1.0 V reaches 227 mAh g−1, which is 52.54% of the total capacity and higher than the values of all previously reported Zn/vanadium oxide batteries. Further study reveals that, compared with the pristine vanadium oxide bronze, the absorption energy for Zn2+ increases from 1.85 to 2.24 eV by cobalt ion intercalation. Furthermore, it also shows a high rate capability (163 mAh g−1 even at 10 A g−1) and extraordinary lifespan over 7500 cycles, with a capacity retention of 90.26%. These performances far exceed those for all reported zinc/vanadium oxide bronze batteries. Subsequently, a nondrying and antifreezing tough flexible battery with a high energy density of 432 Wh kg−1 at 0.1 A g−1 is constructed, and it reveals excellent drying and freezing tolerance. This research represents a substantial advancement in vanadium materials for various battery applications, achieving both a high discharge voltage and high capacity.
Zn/vanadium oxide batteries can deliver a capacity greater than 300 mAh g−1, but their operational voltage is always very low. A 1.7 V high‐voltage Zn/vanadium battery is developed using a Co0.247V2O5 ⋅ 0.944H2O cathode. Its capacity at greater than 1.0 V reaches 227 mAh g−1, which is 52.54% of the total capacity and higher than the values of all previously reported Zn/vanadium oxide batteries.
Lithium–sulfur (Li–S) batteries deliver a high theoretical energy density of 2600 Wh kg−1, and hold great promise to serve as a next‐generation high‐energy‐density battery system. Great progress has ...been achieved in cathode design to deal with the intrinsic problems of sulfur cathodes, including low conductivity, the dissolution of polysulfide intermediate, and volume fluctuation. However, aiming at the practical applications of Li–S batteries, the weight percentage of sulfur in cathode materials and the overall areal sulfur loading need to be significantly increased, which inevitably complicate the process and cause heavy shuttle effect, slow redox kinetics, and more undesirable reaction pathways. Recently, rationally designing efficient mediators, as well as incorporating them into a working battery, emerges to be a promising method to construct high‐energy‐density Li–S batteries. The influence of mediators on Li–S batteries appears to be the enhancement in redox kinetics and the increase in reaction efficiency. In this feature article, the mechanistic understanding of redox kinetics in Li–S reactions is discussed, and then a comprehensive analysis of the recent advances in both heterogeneous and homogeneous mediator design is provided. A mediator perspective in building high‐energy‐density Li–S batteries is also included.
Mediators in lithium–sulfur batteries can enhance the redox kinetics and increase the reaction efficiency, which benefit the practical applications requiring a high sulfur content and a high areal loading amount. This feature article discusses the mechanism of redox kinetics, and reviews the recent advances in heterogeneous/homogeneous mediator design in lithium–sulfur batteries.
Rechargeable lithium metal batteries are next generation energy storage devices with high energy density, but face challenges in achieving high energy density, high safety, and long cycle life. Here, ...lithium metal batteries in a novel nonflammable ionic‐liquid (IL) electrolyte composed of 1‐ethyl‐3‐methylimidazolium (EMIm) cations and high‐concentration bis(fluorosulfonyl)imide (FSI) anions, with sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as a key additive are reported. The Na ion participates in the formation of hybrid passivation interphases and contributes to dendrite‐free Li deposition and reversible cathode electrochemistry. The electrolyte of low viscosity allows practically useful cathode mass loading up to ≈16 mg cm−2. Li anodes paired with lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (LiNi0.8Co0.1Mn0.1O2, NCM 811) cathodes exhibit 99.6–99.9% Coulombic efficiencies, high discharge voltages up to 4.4 V, high specific capacity and energy density up to ≈199 mAh g−1 and ≈765 Wh kg−1 respectively, with impressive cycling performances over up to 1200 cycles. Highly stable passivation interphases formed on both electrodes in the novel IL electrolyte are the key to highly reversible lithium metal batteries, especially for Li–NMC 811 full batteries.
A nonflammable ionic‐liquid electrolyte is developed for high‐safety and high‐energy‐density Li metal batteries, allowing practically useful cathode mass loading up to 16 mg cm−2, realizing high specific capacity and energy density (199 mAh g−1 and 765 Wh kg−1) with impressive cycling performances. The robust passivation interphases formed on both electrodes are key to realizing impressive battery performances.
A hollow graphene/conducting polymer composite fiber is created with high mechanical and electronic properties and used to fabricate novel fiber‐shaped supercapacitors that display high energy ...densities and long life stability. The fiber supercapacitors can be woven into flexible powering textiles that are particularly promising for portable and wearable electronic devices.
The increasing demand for wearable electronic devices necessitates flexible batteries with high stability and desirable energy density. Flexible lithium–sulfur batteries (FLSBs) have been ...increasingly studied due to their high theoretical energy density through the multielectron chemistry of low-cost sulfur. However, the implementation of FLSBs is challenged by several obstacles, including their low practical energy density, short life, and poor flexibility. Various graphene-based materials have been applied to address these issues. Graphene, with good conductivity and flexibility, exhibits synergistic effects with other active/catalytic/flexible materials to form multifunctional graphene-based materials, which play a pivotal role in FLSBs. This review summarizes the recent progress of graphene-based materials that have been used as various FLSB components, including cathodes, interlayers, and anodes. Particular attention is focused on the precise nanostructures, graphene efficacy, interfacial effects, and battery layout for realizing FLSBs with good flexibility, energy density, and cycling stability.
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