MoS3 nanoparticles as well as MoS3 on graphene and multiwalled carbon nanotubes were synthesized by a solvothermal method and the prepared samples were employed as cathode material in zinc-ion ...batteries. With distinct advantages like low price, high safety, no environmental pollution, and high power, these batteries have promising properties for future generation battery systems. The microstructure and electrochemical properties of the prepared composite cathodes were investigated by XRD, TG, and XPS. The MoS3/MWCNTs have a discharge specific capacity of 368 mAh g−1 at the current density of 500 mA g−1 and stable cycling performance, and the discharge specific capacity of MoS3/MWCNTs can still reach 321 mAh g−1 at the current density of 1 A g−1. Making use of the outstanding mechanical, electrochemical and electronic properties of MWCNTs, the coated composite of MoS3 nanoparticles on MWCNTs can significantly improve the electrical conductivity of the materials, and enhance the charge-discharge capacity and high rate characteristics of MoS3 as aqueous zinc-ion cathode material.
•MoS3, MoS3-G, and MoS3-MWCNT were synthesized by a simple solvothermal method.•Carbon-doped MoS3 were uniform growthed on the surface of graphene and MWCNTs.•MoS3-G, and MoS3-MWCNT show a more disordered and higher specific surface structure.•Disordered structure promote the transfer of zinc ions and enhance the charge-discharge capacity.
In this paper, the microstructure and mechanical properties of SLM-Hastelloy X alloy treated by hot isostatic pressing and heat treatment (HIP + HT) were studied. The microscopic characteristics show ...that the grains are transformed into equiaxed grains after different HIP + HT. The precipitates of M23C6 carbide are distributed in grains and grains boundaries. The number of precipitates in grains decreased during the increase of the temperature of the heat treatment. The results of nano-indentation experiments show that the average elastic modulus first increases and decreases with the growth of heat treatment temperature, and the average hardness fluctuates significantly in increasing the temperature of post-treatment. When the heat treatment temperature reaches the maximum value, the minimum value of average hardness is obtained of 2.46 GPa. The Vickers hardness decreases from 204HV0.5 to 188HV0.5 with the increase of heat treatment temperature. According to tensile tests, a good combination of strength and plastic properties of SLM-Hastelloy X alloy after HIP + HT treatment is obtained except for HIP+1150 °C/h.
Preparation schematic of the Sn/SnOx@NC composite powders and the morphology evolution and rate performance of the Sn/SnOx@NC-2 electrode.
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•Heterogeneous Sn/SnOx powders are prepared ...by the disproportionated reaction of SnO.•Plate-like Sn/SnOx is perfectly encapsulated by the N-doped carbon layer.•Sn/SnOx@NC microplates possess heterojunction-induced oxygen vacancies.•Sn/SnOx@NC-2 electrode delivers excellent electrochemical performance.
Heterogeneous Sn/SnOx@N-doped carbon (Sn/SnOx@NC) microplates with oxygen vacancies evolved from plate-like SnO powders are successfully fabricated, in which SnO powders are converted into Sn, SnO2, and Sn2O3 phases by rationally sintering and are perfectly in situ encapsulated by polyaniline-derived NC layer. By elaborately constructing the particular structure, high discharge specific capacity of 730.4 mAh/g and capacity retention ratio of 98.3 % after 110 cycles at 0.1 A/g are realized for optimal Sn/SnOx@NC composite electrode. Benefiting from enhanced electronic conductivity and Li+ ions diffusion kinetics, the assembled cell delivers reversible discharge specific capacity of 487.3 mAh/g at 1.0 A/g after 500 cycles. First principles calculation and in/ex situ characterization reveal that in situ formed heterostructure with oxygen vacancies and NC layer synergistically improve interfacial charge transfer and reaction reversibility to promote lithium storage capability. Therefore, fabricating Sn/SnOx@NC microplates may provide a practical strategy to design heterogeneous and oxygen-deficient Sn-based anode materials for high-performance lithium-ion batteries.
•NiCo2O4 nanosheets rich in oxygen vacancies were synthesized by a simple solvothermal method.•NiCo2O4 nanosheets rich in oxygen vacancies exhibit an excellent cycling and rate capability.•Oxygen ...vacancies promote the transfer of zinc ions and enhance the charge-discharge capacity.
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Aqueous zinc-ion supercapacitors are a new type of energy storage device possessing high energy density, high safety, long service life, and abundant raw materials, which have attracted attention toward research. In this paper, NiCo2O4 nanosheets rich in oxygen vacancies were used as the cathode material for a novel aqueous zinc-ion supercapacitor. The aqueous zinc-ion supercapacitor device showed excellent electrochemical performance with a high specific capacity of 122.5 mAh/g at a current density of 1 A/g. The specific capacity of discharge at a current density of 10 A/g was found to be 72.6 mAh/g, along with a capacity retention rate of 59.3%. The reduction of NaBH4 enhanced the content of oxygen vacancies in the materials, which facilitated the enhancement of the conductivity and electrochemical properties of the materials. The high energy density and high multiplier performance of the aqueous zinc-ion supercapacitors showed potential for wide applications in portable electronic products and smart devices.
•A novel single-end distance protection scheme for HVDC lines is proposed.•This protection is based on the linear distribution of low frequency voltage signals along the line.•Principles of mho relay ...are improved and applied in the new protection.•An internal fault can be detected if the measure voltage is opposite in sign with the compensating voltage.•Compared with other single-end HVDC line protections, this novel method has numerous merits.
HVDC transmission system is becoming increasingly desirable for its obvious technical and environmental advantages. A novel single-end distance protection scheme for HVDC lines is proposed in this paper. It is based on the linear distribution of low frequency voltage signals between the relay point and setting point. An internal fault can be detected if the low-pass filtered measure voltage is opposite in sign with the compensating voltage at the setting point, which can be calculated with the R-L differential-equation algorithm. To find a tradeoff between operating speed and accuracy, the protection is divided into K zones, each of which has different protection scopes and cut-off frequencies. A two-terminal HVDC system and a multi-infeed HVDC system are respectively built in EMTDC. Comprehensive simulation results have indicated that the proposed protection scheme has satisfactory operation performance and will be not influenced by system topologies or parameters. Besides, it is not sensitive to noises or voltage levels. Compared with many other single-end protections for HVDC lines, this novel distance protection has clear setting principles, lower sampling frequency, smaller calculation amount and faster operating speed.
As one of the dominant configurations, platinum (Pt) single atomic catalysts (SACs) have pushed the performance of the hydrogen evolution reaction (HER) to an unprecedented level due to the maximized ...atomic utilization efficiency of Pt atoms. However, the contribution of atomic clusters, which exist in SACs as well, to the overall catalytic performance is always overlooked, thus limiting further enhancement of the performance of Pt-catalyzed HER. Herein, we report anchoring Pt atomic clusters on N-doped graphene for ultrahigh performance of the HER. Benefiting from optimized electron transfer and larger binding energy between active centers and the substrate, Pt atomic cluster catalysts (ACCs) exhibit higher catalytic activity than their single atomic counterparts after 4000 cycles and more than 16 h for HER in an acid solution. These findings reveal a vast opportunity to enhance the catalytic performance of chemical reactions with noble-metal-based ACCs in the near future.
In order to enhance the electrochemical properties of nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode material, lithium-ion conductor shell was coated on the surface of the material through a facile wet ...chemical route. The morphologies, structures and chemical compositions of the samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, energy dispersive spectrometer and X-ray photoelectron spectroscopy. The result shows that the particle surface was uniformly coated by a very thin LaPO4 layer. Electrochemical measurements proved that the LaPO4-coated sample exhibited excellent cycling performance. The capacity retention of LaPO4-coated sample was 91.2% at 1 C after 100 cycles, which was higher compared with that of the pristine sample (76.4%). Moreover, the rate performance of the coated sample was greatly enhanced especially at 2, 5 and 10 C rate. The LaPO4-coated sample showed smaller charge transfer resistance and higher diffusion coefficient of lithium ions compared with those of the pristine sample.
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•LiNi0.8Co0.1Mn0.1O2 microspheres were coated by LaPO4 thin layers.•The interfacial charge transfer resistance became much lower.•Lithium ion diffusion coefficient was remarkably increased.•Cycling and rate performances were significantly improved.
P2-type Na0.67MnO2 with a stable structure and an open framework can provide numerous channels for fast Na+ de/intercalation, for which it is considered to be advantageous in application of the ...cathode material for Na-ion batteries. However, the complex phase transition occurring during cycling and the lattice distortion triggered by the Jahn–Teller effect severely restrict its development. Herein, the modified Na0.67MnO2 with Cu or Fe single-element doping as well as Cu and Fe double-element doping was synthesized by the sol–gel method, and the effects of doping on the crystal structure and electrochemical performances of Na0.67MnO2 were studied. It was demonstrated that the phase of the material did not change after the introduction of Cu and Fe elements, and the cycling stability and rate performance were greatly improved by Cu and Fe double-doping owing to their synergistic effect. The Na0.67Mn0.92Fe0.04Cu0.04O2 (NMFCO) cathode delivers discharge specific capacities of 110.5 mA h g–1 at 5 C and 91.8 mA h g–1 at 10 C and exhibits the high-capacity retention of 94.35% at 1 C and 90.68% at 5 C after 100 cycles. Overall, this study offers a guiding direction for accelerating the modification of P2-type Na0.67MnO2 as a cathode active material for high performance Na-ion batteries.
Li-rich cathode materials have higher discharge capacity and lower cost than conventional electrode materials such as LiCoO2. However, they suffer from rapid capacity fading caused by irreversible ...phase transition and interfacial instability during the electrochemical cycling. La–Co–O (denoted as LC) compound possess good electronic conductivity and superior thermal stability, which could be used as a promising coating layer to suppress Mn dissolution as well as to facilitate electrical transfer. Furthermore, La–Co–O (LC) coating layer could decrease the Mn3+ ions on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 (denoted as LMNC), thus stabilize the surface structure. Herein, we present La–Co–O (LC) coating layer on the surface of LMNC via an artful sol-gel-based method with a thickness below 50 nm. XPS, EDS and TEM tests were applied to confirm the existence of LC coating layer. 2 mol% LC coated LMNC sample shows much improved cycle stability at 1C (206.3 mAh g−1, 86.2% capacity retention after 100 cycles) and good rate capability especially at high rates. In addition, LC coating could effectively suppress voltage fading of LMNC. EIS results reveal that the LC modified LMNC materials exhibit better electrochemical kinetics than the pristine one.
