A flexible N-doped carbon nanofiber membrane loaded with Nb and Ni nanoparticles (Nb/Ni@NC) was prepared using electrospinning technology and a subsequent thermal annealing method and used as a self-supporting anode material for lithium-ion batteries. The Nb/Ni@NC nanofiber membrane had excellent flexibility and could be folded and bent at will without fragmentation and wrinkling; the nanofibers also had a uniform and controllable morphology with a diameter of 300-400 nm. The electrochemical results showed that the flexible Nb/Ni@NC electrode could deliver a high discharge capacity of 378.7 mAh g-1 after 200 cycles at 0.2 A g-1 and an initial coulombic efficiency of 67.7%, which was higher than that of the pure flexible NC anode in contrast. Moreover, a reversible discharge capacity of 203.6 mAh g-1 after 480 cycles at 1.0 A g-1 was achieved by the flexible Nb/Ni@NC electrode with a capacity decay for each cycle of only 0.075%, which showed an excellent rate capability and cycling stability.
Download This Paper Open PDF in Browser Add Paper to My Library Share: Permalink Using these links will ensure access to this page indefinitely Copy URL Copy DOI
Abstract Titanium niobium oxide (TiNb 2 O 7 ) is considered as a promising candidate for lithium‐ion capacitors (LICs) due to its high reversible capacity, low cost, and safety. However, it is limited by ineffective ion diffusivity and low intrinsic conductivity. Herein, in situ defect engineering in TiNb 2 O 7‐ x nanochains is successfully achieved by a facile electro‐spinning technique to improve their electrochemical performance. Remarkably, the oxygen vacancies can enhance the electronic conductivity, while the enlarged lattice spacing is conducive to the Li + insertion/extraction, consequently enhancing the electron and ion transport kinetics. Moreover, such oxygen vacancies and enlarged lattice spacing can supply more active sites for lithium storage. Consequently, the TiNb 2 O 7‐ x nanochains exhibit a remarkable specific capacity of 440 mAh g −1 at 0.1 A g −1 , superior rate capability (126 mAh g −1 at a high current density of 5.0 A g −1 ), and cycling stability (92% retention over 2000 cycles at 1.0 A g −1 ). In addition, the TiNb 2 O 7‐ x ‐based LIC delivers high energy/power densities of 114 Wh kg −1 and 22502.4 W kg −1 with high‐rate performance and long cycle lifespan. This work provides new insights on in situ formation of defects to enhance the electrochemical behavior for high‐rate LICs.
In this paper,we make a study on the grain-yield forecasting model based on time series Normalized Difference Vegetation Index(NDVI) derived from NOAA-AVHRR.We build the grain yield-forecasting model by three different modeling patterns,including Parameter-yield mode,Decomposed yield mode and Difference-yield mode.By comparing the significances of three models,we pick out the final forecasting model for different province.The models were used to predict the autumn grain yield of different province in China and the differences are-4.9% to 11.59% by comparing with the yield data of the National Statistic Bureau,the R Square is 0.947.
Lithiation modification of VO2(B) has been carried out by a facile hydrothermal process, and the compact and locally ordered VO2(B) raft-like nanobelt arrays have been prepared. The synthesis route provides a new approach to elaborate a VO2(B) nanostructure under a mild environment condition. It is found that the growth mechanism of VO2(B) raft-like nanobelt arrays is different from the traditional nucleation-growth process. A novel chemical lithiating-exfoliating-splitting model is proposed. Compared with the bulk counterpart, the lithiated VO2(B) raft-like nanobelt arrays as cathodes exhibit a higher discharge capacity and an enhanced high-rate performance owing to their increased structural anisotropy and decreased polarization. This work indicates that VO2(B) raft-like nanobelt arrays have great potential applications as cathode materials for lithium ion batteries.
Due to the various drawbacks of collecting temperature using embedded or patch thermocouple sensor, the internal temperature estimation is getting more and more attention in the field of lithium power battery. In this paper, the commercial 18650 LiFePO4 battery is selected to analyze the characteristic of Electrochemical Impedance Spectroscopy (EIS) from 0°C to 55°C of 0.1 to 10 000 Hz. The results reveal that there exists intrinsic relationship between the alternating current (AC) impedance phase shift and the internal temperature in the range of 10 to 100 Hz from 5 to 55°C. And the intrinsic relationship is not interfered with the State-of-Charge (SOC) and the State-of-Health (SOH). Subsequently, the relationship is described with a modified Arrhenius equation under the excitation frequency of 12, 44, and 79 Hz. Finally, a novel internal temperature estimation method is proposed by the AC impedance phase shift. The applicability and accuracy of the method are further verified via 10 temperature points. The results indicate that the estimation error is within 1°C in the common operating temperature range (15-45°C), suggesting that the proposed method can be applied to estimate battery internal temperature. Finally, the implementation system of real-time estimation for engineering application is constructed.
Aqueous zinc-ion batteries possess great potential as they offer high safety, low cost, high specific capacity, and long cycle life. However, critical challenges, including dendrite growth, hydrogen evolution, and corrosion, impede their commercialization viability. To address these issues, we propose a solution by introducing succinic acid (SA) to the conventional ZnSO4 electrolyte. The carboxyl groups in SA exhibit excellent coordination capabilities with Zn2+ ions, displacing some active water molecules in the Zn2+ inner solvation shell. This disruption of the hydrogen-bond network, modifies the solvation structure of Zn2+ ions, effectively suppressing hydrogen evolution. Moreover, the carboxyl group forms a strong bond with Zn metal, leading to the preferential adsorption and reaction of Zn2+ to create a Zn-SA composite film on the Zn anode’s surface. This feature reduces by-products, promotes uniform zinc ion deposition, resulting in a symmetric cell assembled with SA additive that can cycle stably for over 4000 hours at 1mA cm-2 and 1mAh cm-2, with an average Coulombic Efficiency of 99.7% during plating/stripping processes. The cell also demonstrates stable cycling for 500 hours at high current densities of up to 10mA cm-2. Zn-V2O5 full cell incorporating SA additive exhibits remarkable rate performance and specific capacity retention over 1000 cycles.
Based on the theory of dynamical clustering,an improved iterative clustering algorithm was brought forward.This iterative clustering algorithm realized on the Microsoft Visual C++ platform by judging the threshold of distance between classes,and had following advantages,such as did not need to predefine initial clustering centers,reduced number of initial parameters to be decided before the classifying,guaranteed more realistic classifying results and made the clustering process easier.In order to validate the practicability of this algorithm,the South Liaoning Province was chosen as a study area,and the moderate resolution satellite data of 250m TERRA MODIS and 250m MERSI of FY3A satellite were used to compared with ISODATA algorithm.The results indicated that the classifying precision of new arithmetic was better,and could be used in classifying remote sensing data.
MCU resource pool is the key technology of the current video conference systems. By enabling flexible and efficient allocation of MCU ports, it greatly improves the reliability of video conference system, and has been widely used in large-scale enterprises. This paper describes the MCU resource pool scheduling strategy in State Grid Corporation, analyzes the key factors of the system, and proposed a quasi-dynamic video conference resource backup strategy optimization method, which can dynamically adapt to changes in the network delay and MCU resources.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)