Full‐temperature all‐solid‐state flexible symmetrical fiber supercapacitors (FSCs) are assembled by using montmorillonite flake/polyvinyl alcohol organic hydrogel (F‐MMT/PVA OHGE) as the electrolyte ...and separator and Ti3C2Tx/ANF‐5% (T/A‐5) fiber as the electrode, in which T/A‐5 fiber is prepared by using delaminated Ti3C2Tx nanosheets as assembled units and 5% of aramid nanofiber (ANF) as the functional additive using a wet spinning method in a coagulated bath with 0.5 m FeCl2 solution. The T/A‐5 hybrid fiber exhibits a specific capacity of 807 F cm−3 in 3 m H2SO4 electrolyte, a superior mechanical strength of 104 MPa, and a high conductivity of 1025 S cm−1. The assembled F‐MMT/PVA OHGE T/A‐5 FSC not only shows a specific capacitance of 295 F cm−3 and a capacitance retention of 91% at a current density of 5 A cm−3 after 10 000 charging/discharging cycles, but also a maximum volumetric energy density of 26.2 mWh cm−3. Meanwhile, the assembled device displays good flexibility and excellent capacitance in a wide temperature range of −40 to 80 °C, the electrochemical performance of the FSC is maintained under varying degrees of bending. This study provides an effective strategy for designing and assembling of full‐temperature all‐solid‐state symmetrical flexible FSCs with the optimal balance of capacitive performance and flexibility.
A Ti3C2Tx/ANF‐5% hybrid fiber with an optimal balance of the capacitance and flexibility is prepared by wet spinning method. A full‐temperature all‐solid‐state fiber supercapacitor is assembled on the basis of the Ti3C2Tx/ANF‐5% fiber and developed organic hydrogel, which shows a maximum volumetric energy density of 26.2 mWh cm−3 and good flexibility in a wide temperature range of ‐40‐80 °C.
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Developing new optimized bifunctional photocatalyst is of great significant for achieving the high‐performance photo‐assisted Li‐O2 batteries. Herein, a novel bifunctional photo‐assisted Li‐O2 system ...is constructed by using siloxene nanosheets with ultra‐large size and few‐layers due to its superior light harvesting, semiconductor characteristic, and low recombination rate. An ultra‐low charge potential of 1.90 V and ultra‐high discharge of 3.51 V have been obtained due to the introduction of this bifunctional photocatalyst into Li‐O2 batteries, and these results have realized the round‐trip efficiency up to 185 %. In addition, this photo‐assisted Li‐O2 batteries exhibits a high rate (129 % round‐trip efficiency at 1 mA cm−2), a prolonged cycling life with 92 % efficiency retention after 100 cycles, and the highly reversible capacity of 1170 mAh g−1 at 0.75 mA cm−2. This work will open the vigorous opportunity for high‐efficiency utilization of solar energy into electric system.
Ultra‐large sized and few layered siloxene nanosheets have been used as a bifunctional photocatalyst in a Li‐O2 battery. Due to its superior photoelectric characters, the assembled photo‐assisted battery has exhibited a breakthrough round‐trip efficiency up to 185 %.
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As a kind of direct-on-line motor, super premium efficiency (IE4) line-start synchronous reluctance motors (LS-SynRMs) were developed recently and are now used in many applications, including fans, ...pumps, and compressors. This paper presents an optimum design and comparative study of LS-SynRMs with additional losses and impact during the manufacturing process (electrical steel cutting/punching damage as well as squirrel-cage die-casting with bubble effects). The work results indicate that the LS-SynRM design with the "manufacturing process loss" effect should be considered and compensated for the design in order to achieve an IE4 class efficiency and ensure synchronization. Furthermore, the LS-SynRM rotor with multilayer flux barriers and rotor slots is investigated in detail. The influences of optimum design geometrical parameters (flux barriers thickness, segments thickness, length of rotor slots, etc.) on the performances of the basic model and optimum design model are evaluated with finite-element analysis (FEA) results. For more accurate results, the effects of saturation, saliency ratio, inductance difference, and the change in the B-H/B-P curve in damaged motor core edges are considered. Meanwhile, in the squirrel cage, the porosity rate distributions are considered. The copper loss, iron loss, starting torque, power factor, efficiency, and synchronization ability are investigated. The experimental results verify the accuracy of the process presented in this paper.
Compared with other flexible energy‐storage devices, the design and construction of the compressible energy‐storage devices face more difficulty because they must accommodate large strain and shape ...deformations. In the present work, CoNi2S4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi2S4 on CNT sponge, in which CoNi2S4 nanoparticles with size among 10–15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g−1. Meanwhile, Fe2O3/CNT sponge anode with specific capacitance of 460 F g−1 in a prolonged voltage window is also prepared by electrodepositing Fe2O3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi2S4/CNT//Fe2O3/CNT) is assembled by using CoNi2S4/CNT sponge as positive electrode and Fe2O3/CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg−1 at a power density of 847 W kg−1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi2S4/CNT//Fe2O3/CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density.
The asymmetric supercapacitor (CoNi2S4/carbon nanotube (CNT)//Fe2O3/CNT) is assembled by using CoNi2S4/CNT sponge as positive electrode and Fe2O3/CNT sponge as negative electrode in 2 m KOH solution. The assembled device exhibits not only excellent energy density of up to 50 Wh kg−1 at a power density of 847 W kg−1, but also shows the structural stability with nearly full recovery from 80% strain.
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Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and ...compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.
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Since the discovery of carbon nanotubes (CNTs), they have drawn considerable research attention and have shown great potential application in many fields due to their unique structural, mechanical, ...and electronic properties. However, their native insolubility severely holds back the process of application. In order to overcome this disadvantage and broaden the scope of their application, chemical functionalization of CNTs has attracted great interest over the past several decades and produced various novel hybrid materials with specific applications. Notably, the rapid development of functionalized CNTs used as electrochemical sensors has been successfully witnessed. In this featured article, the recent progress of electrochemical sensors based on functionalized CNTs is discussed and classified according to modifiers covering organic (oxygen functional groups, small organic molecules, polymers, DNA, protein,
etc.
), inorganic (metal nanoparticles, metal oxide,
etc.
) and organicinorganic hybrids. By employing some representative examples, it will be demonstrated that functionalized CNTs as templates, carriers, immobilizers and transducers are promising for the construction of electrochemical sensors.
Recent progress of electrochemical sensors based on functionalized carbon nanotubes have been discussed and classified according to modifiers.
By using three-dimensional (3D) tubular molybdenum disulfide (MoS2) as both an active material in electrochemical reaction and a framework to provide more paths for insertion and extraction of ions, ...PANI nanowire arrays with a diameter of 10–20 nm can be controllably grown on both the external and internal surface of 3D tubular MoS2 by in situ oxidative polymerization of aniline monomers and 3D tubular MoS2/PANI hybrid materials with different amounts of PANI are prepared. A controllable growth of PANI nanowire arrays on the tubular MoS2 surface provides an opportunity to optimize the capacitive performance of the obtained electrodes. When the loading amount of PANI is 60%, the obtained MoS2/PANI-60 hybrid electrode not only shows a high specific capacitance of 552 F/g at a current density of 0.5 A/g, but also gives excellent rate capability of 82% from 0.5 to 30 A/g. The remarkable rate performance can be mainly attributed to the architecture with synergistic effect between 3D tubular MoS2 and PANI nanowire arrays. Moreover, the MoS2/PANI-60 based symmetric supercapacitor also exhibits the excellent rate performance and good cycling stability. The specific capacitance based on the total mass of the two electrodes is 124 F/g at a current density of 1 A/g and 79% of its initial capacitance is remained after 6000 cycles. The 3D tubular structure provides a good and favorable method for improving the capacitance retention of PANI electrode.
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Development of highly stabilized and reversible cathode materials has become a great challenge for sodium‐ion batteries. O′3‐type layered Mn‐based oxides have deserved much attention as one of ...largely reversible‐capacity cathodes featured by the resource‐rich and low‐toxic elements. However, the fragile slabs structure of typical layered oxides, low Mn‐ion migration barriers, and Jahn–Teller distortion of Mn3+ have easily resulted in the severe degradation of cyclability and rate performances. Herein, a new queue‐ordered superstructure is built up in the O′3‐NaMn0.6Al0.4O2 cathode material. Through the light‐metal Al substitution in O′3‐NaMnO2, the MnO6 and AlO6 octahedrons display the queue‐ordered arrangements in the transition metal (TM) slabs. Interestingly, the presence of this superstructure can strengthen the layered structure, reduce the influence from Jahn–Teller effect, and suppress the TM‐ions migrations during long‐terms cycles. These characteristics results in O′3‐NaMn0.6Al0.4O2 cathode deliver a high capacity of 160 mAh g−1, an enhanced rate capability and the excellent cycling performance. This research strategy can provide the broaden insight for future electrode materials with high‐performance sodium‐ions storage.
A novel queue‐order NaMn0.6Al0.4O2 (NMA) is first prepared as high‐performance cathode material for sodium‐ion battery. The NMA exhibits a firmed layered structure based on queue‐ordered Mn0.6Al0.4O2 slabs, which result in NMA cathode delivers a high practical capacity of 160 mAh g−1, a remarkable rate performance and an excellent cycling life of 81% retention after 100 cycles.
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In this article, a new broadband circularly polarized (CP) microstrip patch antenna (MPA) with a sequential phase (SP) square‐loop feeding structure is proposed. The presented antenna is composed of ...a square‐loop feeding structure, four L‐shaped parasitic patches with L‐shaped slots, four parasitic square patches, and a corner‐truncated square patch. At first, a SP square‐loop is designed as a feeding structure. Then, four L‐shaped parasitic patches with L‐shaped slots are utilized to generate one CP mode by a capacitive coupled way. At last, four parasitic square patches and a corner‐truncated square patch are together placed above the SP feeding structure to broaden the circularly polarized bandwidth (CPBW). The presented antenna has a wide 3‐dB axial ratio bandwidth (ARBW) of 16.7% (5.4 GHz, 4.95‐5.85 GHz), and a wide 10‐dB return loss bandwidth of 25.5% (5.5 GHz, 4.8‐6.2 GHz). The proposed antenna features compact structure and broad 3‐AR bandwidth which could completely cover the WLAN (5.725‐5.85GHz) band. Therefore, the proposed antenna is suitable for circular polarization applications in C band.
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Polyacrylonitrile/Boric acid/Melamine/the delaminated BN nanosheets electrospun fiber membrane (PB
N
BN) with excellent mechanical property, high thermal stability, superior flame-retardant ...performance, and good wettability are fabricated by electrospinning PAN/DMF/H
BO
/C
H
N
/ the delaminated BN nanosheets (BNNSs) homogeneous viscous suspension and followed by a heating treatment. BNNSs are obtained by delaminating the bulk h-BN in isopropyl alcohol (IPA) with an assistance of Polyvinylpyrrolidone (PVP). Benefiting from the cross-linked pore structure and high-temperature stability of BNNSs, PB
N
BN electrospun fiber membrane delivers high thermal dimensional stability (almost no size contraction at 200 °C), excellent mechanical property (19.1 MPa), good electrolyte wettability (contact angle about 0°), and excellent flame retardancy (minimum total heat release of 3.2 MJ m
). Moreover, the assembled LiFePO
/PB
N
BN/Li asymmetrical battery using LiFePO
as the cathode and Li as the anode has a high capacity (169 mAh g
at 0.5 C), exceptional rate capability (129 mAh g
at 5 C), the prominent cycling stability without obvious decay after 400 cycles, and a good discharge capacity of 152 mAh g
at a high temperature of 80 °C. This work offers a new structural design strategy toward separators with excellent mechanical performance, good wettability, and high thermal stability for lithium-ion batteries.
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