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Showing papers on "Power density published in 2019"


Journal ArticleDOI
TL;DR: In this article, the authors fabricated porous hollow carbon spheres with different morphologies and electrochemical properties using yeast cell templates, and the as-prepared sample exhibited an ultrahigh specific capacitance of 255 F g 1 at a current density 1 A g 1 in 1 M Na2SO4 electrolyte.

345 citations


Journal ArticleDOI
TL;DR: In this paper, a flexible solid-state zinc ion hybrid supercapacitor (ZHS) based on co-polymer derived hollow carbon spheres (HCSs) as the cathode, polyacrylamide (PAM) hydrogel as the electrolyte and Zn deposited on carbon cloth as the anode.
Abstract: High electrochemical performance energy storage devices coupled with low cost and high safety operation are in urgent need due to the increasing demand for flexible and wearable electronics. For these applications lithium-ion and sodium-ion batteries are vastly limited due to their relatively low power density and security risks. On the other hand, conventional supercapacitors are suitable for flexible and wearable electronics due to their high power density while their low energy density has hindered their wide applications. Lithium or sodium ion hybrid supercapacitors are promising energy storage devices that benefit from the combined high energy density of batteries and high power density of supercapacitors. However, the use of organic electrolytes and shortage of lithium resources are expected to limit their widespread commercialization for flexible and wearable electronics. Here, for the first time, we introduce a safe and flexible solid-state zinc ion hybrid supercapacitor (ZHS) based on co-polymer derived hollow carbon spheres (HCSs) as the cathode, polyacrylamide (PAM) hydrogel as the electrolyte and Zn deposited on carbon cloth as the anode. Owing to the high surface area of the HCSs and the hollow structure which improves the ion adsorption and desorption kinetics of the cathode, the flexible solid-state ZHS delivers a highest capacity of 86.8 mA h g−1 and a maximum energy density of 59.7 W h kg−1 with a power density of 447.8 W kg−1. Besides, it displays excellent cycling stability with 98% capacity retention over 15 000 cycles at a current density of 1.0 A g−1. Moreover, the solid-state ZHS is flexible enough to sustain various deformations including squeezing, twisting and folding due to the use of flexible electrodes and electrolytes. Our study unveils a pioneering flexible solid-state ZHS with high safety, which is a promising candidate for flexible and wearable energy storage devices.

215 citations


Journal ArticleDOI
TL;DR: In this article, an isolated 25 kW, 48 kHz, 7 kV to 400 V series resonant dc/dc converter based on 10 kV SiC MOSFETs is realized and tested.
Abstract: The power supply chain of data centers from the medium voltage (MV) utility grid down to the chip-level voltage consists of many series connected power conversion stages and accordingly shows a relatively low efficiency. Solid-state transformers (SSTs) could improve the efficiency by substantially reducing the number of power conversion stages and/or directly interfacing the MV ac grid to a 400 V dc bus, from where server racks with a power consumption of several tens of kilowatts could be supplied by individual SSTs. The recent development of SiC MOSFETs with a blocking voltage of 10 kV enables the realization of a simple and, hence, highly reliable two-stage SST topology, consisting of an ac/dc power factor correction rectifier and a subsequent isolated dc/dc converter. In this context, an isolated 25 kW, 48 kHz, 7 kV to 400 V series resonant dc/dc converter based on 10 kV SiC MOSFETs is realized and tested in this paper. To achieve zero voltage switching of all MOSFETs, a special modulation scheme to actively control the amount of the switched magnetizing current on the MV- and low voltage-sides is implemented. Furthermore, the design of all main components and, especially, the electrical insulation of the employed medium-frequency transformer are discussed in detail. Calorimetric efficiency measurements show that a full-load efficiency of 99.0% is achieved, while the power density reaches 3.8 kW/L ( $63~\text {W}/\mathrm {in^{3}}$ ).

195 citations


Journal ArticleDOI
TL;DR: In this article, a new high-density polyethylene (HDPE)-based radiation-grafted anion exchange membrane (RG-AEM) was proposed, which achieves a surprisingly high peak power density and a low in situ degradation rate.
Abstract: Herein we detail the development of a new high-density polyethylene-(HDPE)-based radiation-grafted anion-exchange membrane (RG-AEM) that achieves a surprisingly high peak power density and a low in situ degradation rate (with configurations tailored to each). We also show that this new AEM can be successfully paired with an exemplar non-Pt-group cathode.

194 citations


Journal ArticleDOI
TL;DR: The factors that influence the co-intercalation potential of graphite are investigated and the tuning of the voltage as large as 0.38 V is achievable by adjusting the relative stability of ternary graphite intercalation compounds and the solvent activity in electrolytes.
Abstract: Co-intercalation reactions make graphite as promising anodes for sodium ion batteries, however, the high redox potentials significantly lower the energy density. Herein, we investigate the factors that influence the co-intercalation potential of graphite and find that the tuning of the voltage as large as 0.38 V is achievable by adjusting the relative stability of ternary graphite intercalation compounds and the solvent activity in electrolytes. The feasibility of graphite anode in sodium ion batteries is confirmed in conjunction with Na1.5VPO4.8F0.7 cathodes by using the optimal electrolyte. The sodium ion battery delivers an improved voltage of 3.1 V, a high power density of 3863 W kg−1both electrodes, negligible temperature dependency of energy/power densities and an extremely low capacity fading rate of 0.007% per cycle over 1000 cycles, which are among the best thus far reported for sodium ion full cells, making it a competitive choice in large-scale energy storage systems. Graphite is a promising anode material for sodium-ion batteries but suffers from the high co-intercalation potential. Here, the authors examine the factors influencing this potential and tailor the stability of graphite intercalation compound, realizing high energy and power densities.

174 citations


Journal ArticleDOI
TL;DR: A finite state machine based management strategy is first proposed for both the battery/ fuel cell and battery/supercapacitor/fuel cell system and results indicate that the proposed method is able to guarantee the required power during most of the driving cycles.

156 citations


Journal ArticleDOI
07 Jan 2019-ACS Nano
TL;DR: The design of T-TENG provides an innovative and effective approach toward large-scale blue energy harvesting by connecting more blocks to form T- TENG networks by supporting that the power density increases proportionally with the number of units connected in parallel without rectifiers.
Abstract: Wave energy is one of the most available energy sources in oceans. In this work, a design of high power density triboelectric nanogenerator (TENG) based on a tower structure is proposed for harvesting wave energy from arbitrary directions. Such tower-like TENG (T-TENG) consists of multiple units made of polytetrafluoroethylene balls and three-dimensional printed arc surface coated with melt adhesive reticulation nylon film. The power generation model coupled with the kinetic model for the T-TENG is proposed and discussed. The T-TENG can effectively convert arbitrary directional wave energy into electrical energy by utilizing charged balls rolling on an optimized arc surface due to ocean wave excitation. In addition, it is found that the power density of the present T-TENG increases linearly from 1.03 W/m3 to 10.6 W/m3 by increasing the units from 1 to 10 in one block. This supports that the power density of the T-TENG increases proportionally with the number of units connected in parallel without rectifie...

155 citations


Journal ArticleDOI
Xuefan Zhou1, H.Y. Qi1, Zhongna Yan1, Guoliang Xue1, Hang Luo1, Dou Zhang1 
TL;DR: The diffuse phase transition from R3c to P4bm phase on heating is considered to be responsible for the superior thermal stability of the high WD and PD, which implies the large potential of the 0.80BNT-0.20NT ceramic in temperature-stable dielectric capacitor applications.
Abstract: Thermal-stable dielectric capacitors with high energy density and power density have attracted increasing attention in recent years. In this work, (1 - x)Bi0.5Na0.5TiO3-xNaTaO3 [(1 - x)BNT-xNT, x = 0-0.30] lead-free relaxor ferroelectric ceramics are developed for capacitor applications. The x = 0.20 ceramic exhibits superior thermal stability of discharged energy density (WD) with a variation of less than 10% in an ultrawide temperature range of -50 to 300 °C, showing a significant advantage compared with the previously reported ceramic systems. The WD reaches 4.21 J/cm3 under 38 kV/mm at room temperature. Besides, a record high of power density (PD ≈ 89.5 MW/cm3) in BNT-based ceramics is also achieved in x = 0.20 ceramic with an excellent temperature insensitivity within 25-160 °C. The x = 0.20 ceramic is indicated to be an ergodic relaxor ferroelectric with coexisted R3c nanodomains and P4bm polar nanoregions at room temperature, greatly inducing large maximum polarization, maintaining low remnant polarization, and thus achieving high WD and PD. Furthermore, the diffuse phase transition from R3c to P4bm phase on heating is considered to be responsible for the superior thermal stability of the high WD and PD. These results imply the large potential of the 0.80BNT-0.20NT ceramic in temperature-stable dielectric capacitor applications.

154 citations


Journal ArticleDOI
Siliang Wang1, Qiang Wang1, Wei Zeng1, Min Wang1, Limin Ruan1, Yanan Ma2 
TL;DR: The proposed zinc-ion capacitor (ZIC) can avoid the insecurity issues that frequently occurred in lithium-ion and sodium-ion capacitors in organic electrolytes and provides an essential strategy for designing next-generation high-performance energy storage devices.
Abstract: Restricted by their energy storage mechanism, current energy storage devices have certain drawbacks, such as low power density for batteries and low energy density for supercapacitors. Fortunately, the nearest ion capacitors, such as lithium-ion and sodium-ion capacitors containing battery-type and capacitor-type electrodes, may allow achieving both high energy and power densities. For the inspiration, a new zinc-ion capacitor (ZIC) has been designed and realized by assembling the free-standing manganese dioxide–carbon nanotubes (MnO2–CNTs) battery-type cathode and MXene (Ti3C2Tx) capacitor-type anode in an aqueous electrolyte. The ZIC can avoid the insecurity issues that frequently occurred in lithium-ion and sodium-ion capacitors in organic electrolytes. As expected, the ZIC in an aqueous liquid electrolyte exhibits excellent electrochemical performance (based on the total weight of cathode and anode), such as a high specific capacitance of 115.1 F g−1 (1 mV s−1), high energy density of 98.6 Wh kg−1 (77.5 W kg−1), high power density of 2480.6 W kg−1 (29.7 Wh kg−1), and high capacitance retention of ~ 83.6% of its initial capacitance (15,000 cycles). Even in an aqueous gel electrolyte, the ZIC also exhibits excellent performance. This work provides an essential strategy for designing next-generation high-performance energy storage devices.

134 citations


Journal ArticleDOI
01 Nov 2019-Small
TL;DR: This work has demonstrated the first quasisolid-state Zn-ion hybrid FC (ZnFC) based on three rationally designed components, which offers high ionic conductivity and excellent stretchability and is applied in wearable electronics.
Abstract: Emerging wearable electronics require flexible energy storage devices with high volumetric energy and power densities. Fiber-shaped capacitors (FCs) offer high power densities and excellent flexibility but low energy densities. Zn-ion capacitors have high energy density and other advantages, such as low cost, nontoxicity, reversible Faradaic reaction, and broad operating voltage windows. However, Zn-ion capacitors have not been applied in wearable electronics due to the use of liquid electrolytes. Here, the first quasisolid-state Zn-ion hybrid FC (ZnFC) based on three rationally designed components is demonstrated. First, hydrothermally assembled high surface area and conductive reduced graphene oxide/carbon nanotube composite fibers serve as capacitor-type positive electrodes. Second, graphite fibers coated with a uniform Zn layer work as battery-type negative electrodes. Third, a new neutral ZnSO4 -filled polyacrylic acid hydrogel act as the quasisolid-state electrolyte, which offers high ionic conductivity and excellent stretchability. The assembled ZnFC delivers a high energy density of 48.5 mWh cm-3 at a power density of 179.9 mW cm-3 . Further, Zn dendrite formation that commonly happens under high current density is efficiently suppressed on the fiber electrode, leading to superior cycling stability. Multiple ZnFCs are integrated as flexible energy storage units to power wearable devices under different deformation conditions.

133 citations


Journal ArticleDOI
TL;DR: In this article, a MOF-based Co-Fe mixed metal oxide (Co3O4/Fe2O3) nanocubes (denoted as CFNC) is applied as both anode and cathode for high-performance symmetric supercapacitors, exhibiting high energy density of 35.15

Journal ArticleDOI
TL;DR: In this article, a NiCo-LDH/Mn3O4 composite is synthesized on nickel foam substrate through a two-step electrodepositon process, which demonstrates a high specific capacity of 1.86 C/cm−2 (1034.33 C/g−1) at the current density of 1

Journal ArticleDOI
TL;DR: In this article, the authors investigated the internal components and cell engineering of nine cylindrical cells, with different power and energy ratios, and found that the coat weights and areal capacities were lower for high power cells.
Abstract: Commercial lithium ion cells are now optimised for either high energy density or high power density. There is a trade off in cell design between the power and energy requirements. A tear down protocol has been developed, to investigate the internal components and cell engineering of nine cylindrical cells, with different power–energy ratios. The cells designed for high power applications used smaller particles of the active material in both the anodes and the cathodes. The cathodes for high power cells had higher porosities, but a similar trend was not observed for the anodes. In terms of cell design, the coat weights and areal capacities were lower for high power cells. The tag arrangements were the same in eight out of nine cells, with tags at each end of the anode, and one tag on the cathode. The thicknesses of the current collectors and separators were based on the best (thinnest) materials available when the cells were designed, rather than materials optimised for power or energy. To obtain high power, the resistance of each component is reduced as low as possible, and the lithium ion diffusion path lengths are minimised. This information illustrates the significant evolution of materials and components in lithium ion cells in recent years, and gives insight into designing higher power cells in the future.

Journal ArticleDOI
01 Mar 2019
TL;DR: In this article, a DAB-based three-phase dc-dc isolated converter with a novel modulation strategy is presented, which results in single-stage power conversion with no electrolytic capacitor.
Abstract: In vehicle-to-grid applications, the battery charger of the electric vehicle (EV) needs to have a bidirectional power flow capability. Galvanic isolation is necessary for safety. An ac–dc bidirectional power converter with high-frequency isolation results in high power density, a key requirement for an on-board charger of an EV. Dual-active-bridge (DAB) converters are preferred in medium power and high voltage isolated dc–dc converters due to high power density and better efficiency. This paper presents a DAB-based three-phase ac–dc isolated converter with a novel modulation strategy that results in: 1) single-stage power conversion with no electrolytic capacitor, improving the reliability and power density; 2) open-loop power factor correction; 3) soft-switching of all semiconductor devices; and 4) a simple linear relationship between the control variable and the transferred active power. This paper presents a detailed analysis of the proposed operation, along with simulation results and experimental verification.

Journal ArticleDOI
Bin Li1, Qiang Li1, Fred C. Lee1
TL;DR: In this article, a novel PCB winding based magnetic structure is proposed to integrate both inductor and transformer into one component, which can be easily controlled by changing the cross-sectional area of the core or the length of the air gap.
Abstract: The momentum toward high power density high-efficiency power converters continues unabated. The key to reducing the size of power converters is high-frequency operation and the bottleneck is the magnetic components. With the emerging widebandgap devices, the switching frequency of power converters increases significantly, to hundreds of kilohertz, which provides us the opportunity to adopt printed circuit board (PCB) winding planar magnetics. Compared with the conventional litz-wire-based magnetics, planar magnetics can not only effectively reduce the converter size, but also offer improved reliability through automated manufacturing process with repeatable parasitics. Another way to reduce the number of magnetic components and shrink the size of power converters is through the magnetic integration. In this paper, a novel PCB winding based magnetic structure is proposed to integrate both inductor and transformer into one component. In this structure, the inductor value can be easily controlled by changing the cross-sectional area of the core or the length of the air gap. A 6.6-kW 500-kHz CLLC resonant converter prototype with 98% efficiency and 130-W/in3 (8 kW/L) power density is built to verify the feasibility of the proposed PCB winding based magnetic structure.

Journal ArticleDOI
TL;DR: In this paper, single phase PbHfO3 antiferroelectric ceramics were prepared via rolling process, which can reduce the grain size and increase the bulk density, which lead to the enhanced breakdown strength up to 268 ǫkV/cm versus 219 kv/cm of samples using the conventional solid-state method.
Abstract: Single phase PbHfO3 antiferroelectric ceramics were prepared via rolling process. It is revealed that the rolling process can reduce the grain size and increase the bulk density, which lead to the enhanced breakdown strength up to 268 kV/cm versus 219 kV/cm of samples using the conventional solid-state method. As a result, high recoverable energy density of 7.6 J/cm3 with an efficiency of 80.8 % was achieved. Meanwhile, a large current density of 1381 A/cm2 and an ultrahigh peak power density up to 170 MW/cm3 were observed under 250 kV/cm. In addition, unique electrical polarization response characteristics at different electric fields and temperature-induced structural phase transitions were also investigated. The energy storage performance and charge-discharge properties of PbHfO3 were first studied in this communication and all the results indicate that PbHfO3 ceramic is a promising candidate for pulse power applications.

Journal ArticleDOI
TL;DR: In this article, the authors explored the impact of thermal integration on photo-electrochemical devices driven by concentrated solar irradiation and design one that operates with high efficiency and power density output.
Abstract: Achieving high current densities while maintaining high energy conversion efficiency is one of the main challenges for enhancing the competitiveness of photo-electrochemical devices. We describe a concept that allows this challenge to be overcome by operating under concentrated solar irradiation (up to 474 kW m−2), using thermal integration, mass transport optimization and a close electronic integration between the photoabsorber and electrocatalyst. We quantify the increase in the theoretical maximum efficiencies resulting from thermal integration, and experimentally validate the concept using a III–V-based photoabsorber and IrRuOx–Pt-based electrocatalysts. We reach current densities higher than 0.88 A cm−2 at calculated solar-to-hydrogen conversion efficiencies above 15%. Device performance, dynamic response and stability are investigated, demonstrating the ability to produce hydrogen stably under varying conditions for more than two hours. The current density and output power (27 W) achieved provide a pathway for device scalability aimed towards the large-scale deployment of photo-electrochemical hydrogen production. For photo-electrochemical hydrogen production to become viable on a large scale, not only efficiency but also power density must be optimized. Here, the authors explore the impact of thermal integration on photo-electrochemical devices driven by concentrated solar irradiation and design one that operates with high efficiency and power density output.

Journal ArticleDOI
TL;DR: In this article, a series of new cathodes for proton-conducting solid oxide fuel cells (SOFCs) were designed and characterized, which can provide a new life for the traditional BaFeO3-based cathodes.
Abstract: Bi and Sn co-doped perovskite BaFe0.8−XSn0.2BiXO3−δ materials have been designed and characterized as a series of new cathodes for proton-conducting solid oxide fuel cells (SOFCs), providing a new life for the traditional BaFeO3-based cathodes. Proton uptake of the cathode increases significantly with bismuth-doping, favoring the application of Bi and Sn co-doped perovskite BaFe0.8−XSn0.2BiXO3−δ materials in proton-conducting SOFCs. The density functional theory (DFT) calculation also suggests that the bismuth-doping leads to a dramatic increase of hydration energy and acceleration of proton migration for the BFS material. The XPS results show that the oxygen reduction reaction (ORR) activity of the cathode is enhanced after bismuth is added, which is consistent with the experimental results of the power density of the single cell. The maximum power density of the single cells with the structure of NiO-BaZr0.1Ce0.7Y0.2O3−δ|BaZr0.1Ce0.7Y0.2O3−δ| BaFe0.5Sn0.2Bi0.3O3−δ (BFSBi0.3) reached 1277 mW cm−2 at 700 °C, which is a record-high performance for proton-conducting SOFCs using cobalt-free cathodes, compared with previous reports. The outstanding fuel cell performance and good long term stability indicate that bismuth-doping is an effective way of promoting proton-conduction in traditional cathodes. This study opens a new door to the design of high performance cathodes for proton-conducting SOFCs.

Journal ArticleDOI
01 Feb 2019-ACS Nano
TL;DR: A binder-free electrode that interconnects carbon-sheathed porous silicon nanowires into a coral-like network and shows fast charging performance coupled to high energy and power densities when integrated into a full cell with a high areal capacity loading is reported.
Abstract: Fast charging rate and large energy storage are becoming key elements for the development of next-generation batteries, targeting high-performance electric vehicles. Developing electrodes with high volumetric and gravimetric capacity that could be operated at a high rate is the most challenging part of this process. Using silicon as the anode material, which exhibits the highest theoretical capacity as a lithium-ion battery anode, we report a binder-free electrode that interconnects carbon-sheathed porous silicon nanowires into a coral-like network and shows fast charging performance coupled to high energy and power densities when integrated into a full cell with a high areal capacity loading. The combination of interconnected nanowires, porous structure, and a highly conformal carbon coating in a single system strongly promotes the reaction kinetics of the electrode. This leads to fast-charging capability while maintaining the integrity of the electrode without structural collapse and, thus, stable cycling performance without using binder and conductive additives. Specifically, this anode shows high specific capacities (over 1200 mAh g-1) at an ultrahigh charging rate of 7 C over 500 charge-discharge cycles. When coupled with a commercial LiCoO2 or LiFePO4 cathode in a full cell, it delivers a volumetric energy density of 1621 Wh L-1 with a LiCoO2 cathode and a power density of 7762 W L-1 with a LiFePO4 cathode.

Journal ArticleDOI
TL;DR: In this paper, an electrochemical-thermal coupling model was established for an 18.5 A h lithium-ion battery, and the model was validated by experiment at four discharge rates.
Abstract: Electrodes are the most important components in the lithium-ion battery, and their design, which ultimately determines the quantity and speed of lithium storage, directly affects the capacity, power density, and energy density of the battery. Herein, an electrochemical–thermal coupling model was established for an 18.5 A h lithium-ion battery, and the model was validated by experiment at four discharge rates. Based on this model, the effects of the electrode design parameters (electrode thickness, volume fraction of active material and particle size) on the battery performance (electrochemical characteristics, thermal behavior, energy density and power density) were initially investigated. It was found that as the electrode thickness and volume fraction of the active material increased, the polarization, heat generation rate and energy density increased, while the power density degraded. In addition, as the particle size decreased, both the energy density and power density improved, which can provide guidance for the design of electrodes. Subsequently, a multi-parameter (thickness of the positive and negative electrodes) and multi-objective (energy density and power density) optimization procedure was performed via two optimization methods, and the positive electrode thickness of 55.335 μm and negative electrode thickness of 63.188 μm were determined to be the optimized parameters.


Journal ArticleDOI
TL;DR: The experimental and simulation analysis show that the dominating capacitance mechanism for the high Na-ion storage performance is due to abundant grain boundaries, three exposed layer interfaces, and carbon wiring in the design.
Abstract: The sodium-ion battery is a promising battery technology owing to its low price and high abundance of sodium. However, the sluggish kinetics of sodium ion makes it hard to achieve high-rate performance, therefore impairing the power density. In this work, a fiber-in-tube Co9 S8 -carbon(C)/Co9 S8 is designed with fast sodiation kinetics. The experimental and simulation analysis show that the dominating capacitance mechanism for the high Na-ion storage performance is due to abundant grain boundaries, three exposed layer interfaces, and carbon wiring in the design. As a result, the fiber-in-tube hybrid anode shows a high specific capacity of 616 mAh g-1 after 150 cycles at 0.5 A g-1 . At 1 A g-1 , a capacity of ca. 451 mAh g-1 can be achieved after 500 cycles. More importantly, a high energy density of 779 Wh kg-1 and power density of 7793 W kg-1 can be obtained simultaneously.

Journal ArticleDOI
TL;DR: In this article, a facile synthesis of high-performance asymmetric supercapacitors with hybrid nickel phosphides/nickel foam as positive electrode and biomass-based sulfur-doped hierarchical porous activated carbon as negative electrodes was reported.

Journal ArticleDOI
Xinru Han1, Qun Chen1, Hong Zhang1, Yonghong Ni1, Li Zhang1 
TL;DR: In this paper, NiCo2S4/Co9S8 hollow spheres were synthesized by using the carbon spheres as the sacrificial template via the solvothermal method and anion exchange process.

Journal ArticleDOI
TL;DR: In this article, an asymmetric supercapacitor with a novel porous carbon nanofiber derived from hypercrosslinked polymers (HCP-CNF) and two-dimensional copper cobalt oxide nanosheets (CCO-NS) as the negative and positive electrodes, respectively, is presented.

Journal ArticleDOI
TL;DR: In this paper, a self-sacrificed route to construct three dimensional conductive vanadium-based MOFs (V-MOFs, MIL-47) nanowire-bundle arrays on carbon nanotube fibers as advanced cathodes for aqueous Zn-ion batteries was reported.

Journal ArticleDOI
TL;DR: In this article, a 1MW 3L-ANPC topology was developed to achieve high efficiency and high power density in a hybrid-electric propulsion system, where the switching devices operating at carrier frequency were configured by the emerging silicon carbide (SiC) metaloxide-semiconductor field effect transistors, while the conventional silicon insulated-gate bipolar transistors were selected for switches operating at the fundamental output frequency.
Abstract: A hybrid-electric propulsion system is an enabling technology to make the aircraft more fuel saving, quieter, and lower carbide emission. In this article, a megawatt (MW) scale power inverter based on a three-level active neutral-point-clamped (3L-ANPC) topology will be developed. To achieve high efficiency, the switching devices operating at carrier frequency in the power converter are configured by the emerging silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors, while the conventional silicon (Si) insulated-gate bipolar transistors are selected for switches operating at the fundamental output frequency. To obtain high power density, dc bus voltage is increased from the conventional 270 V to medium voltage of 2.4 kV to reduce cable weight. Also, unlike the traditional 400 Hz dominated aircraft ac systems, the rated fundamental output frequency here is boosted to 1.4 kHz to drive the high-speed motor, which helps further to reduce the motor weight. Main hardware development and control modulation strategies are presented. Experimental results are presented to verify the performance of this MW-scale medium-voltage “SiC+Si” hybrid 3L-ANPC inverter. It is shown that the 1-MW 3L-ANPC inverter can achieve a high efficiency of 99% and a high power density of 12 kVA/kg.

Journal ArticleDOI
TL;DR: The synergistic effects of the core-shell CoMoO4@NiCo2S4@NF electrode material highlight the potential of this composite as an effective active material for supercapacitor applications.
Abstract: Supercapacitors are one of the most promising renewable-energy storage systems. In this study, a three-dimensional walking palm-like core–shell CoMoO4@NiCo2S4@nickel foam (NF) nanostructure was synthesized using a two-step hydrothermal method for high electrochemical performance. The as-prepared composite exhibited a high areal capacitance of 17.0 F cm−2 (2433 F g−1) at a current density of 5 mA cm−2 in a three-electrode system. The results revealed outstanding cycling stability of 114% after 10 000 charge–discharge cycles. An aqueous asymmetric supercapacitor device assembled with CoMoO4@NiCo2S4@NF and activated carbon (AC)@NF as the positive and negative electrodes, respectively, showed a high capacitance of 4.19 F cm−2 (182 F g−1) and delivered a high energy density of 60.2 W h kg−1 at a power density of 188 W kg−1 and a high power density of 1.5 kW kg−1 at an energy density 29.2 W h kg−1, lighting 22 parallel-connected red light emitting diodes for over 60 s. The synergistic effects of the core–shell CoMoO4@NiCo2S4@NF electrode material highlight the potential of this composite as an effective active material for supercapacitor applications.

Journal ArticleDOI
TL;DR: In this article, a binder-free electrode material for pseudocapacitors, CoNiSe2, was synthesized on Ni foam via simple solvothermal method.

Journal ArticleDOI
TL;DR: In this paper, a three-dimensional macroporous antimony@carbon composite (Sb@C-3DP) is fabricated by a simple KCl template method with a single bi-functional precursor potassium antimony tartrate.
Abstract: Potassium-ion batteries (KIBs) are considered important substitutes for lithium-ion batteries (LIBs) owing to the abundance of K resources. Herein, a novel three-dimensional macroporous antimony@carbon composite (Sb@C-3DP) is fabricated by a simple KCl template method with a single bi-functional precursor potassium antimony tartrate. The Sb@C-3DP electrode delivers an excellent rate capability (286 mA h g−1 at 1 A g−1) and remarkable reversible capacity (516 mA h g−1 at a low current density of 0.05 A g−1). Moreover, an outstanding long-term cycling stability (97% capacity retention after 260 cycles) is also achieved, which is benefited from the unique microstructure that can accommodate the huge volumetric change of Sb during depotassiation and potassiation processes. A full cell constructed by coupling Sb@C-3DP with a Prussian blue cathode exhibits a high energy density (197.6 W h kg−1) and power density (2067.9 W kg−1).