Papers by Keyword: Carbon Coating

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Authors: Xiang Yin Mo, Xiao San Feng, Yi Ding, Cai Rong Kang
Abstract: Carbon-coated, bismuth-doped, lithium iron phosphates, LiFe1xBixPO4 (0x0.05), have been synthesized by a solid-state reaction method. From the optimization, the carbon-coated LiFe0.95Bi0.05PO4 phase showed superior performances in terms of phase purity and high discharge capacity. The structural, morphological, and electrochemical properties were studied and compared to carbon-coated, LiFePO4. The Li/LiFe0.95Bi0.05PO4 with carbon coating cell delivered an initial discharge capacity of 145 mAh/g and was 30 mAh/g higher than the Li/LiFePO4 with carbon coating cell. Cyclic voltammetry revealed excellent reversibility of the LiFe0.95Bi0.05PO4 with carbon coating material. High rate capability studies were also performed and showed a capacity retention over 93% during the cycling. It was concluded that substituted Bi ion play an important role in enhancing battery performance of the LiFePO4 material through improving the kinetics of the lithium insertion/extraction reaction on the electrode.
Authors: János Ginsztler, László Major, Zsolt Puskás, Margit Koós, János Dobránszky, Michael Giese, Barnabás Szabó, Katalin Albrecht
Authors: Cui Xia Liu, Yan Qing Yang, Xian Luo
Abstract: The tensile strengths of carbon-coated and non carbon-coated SiC filament by Chemical Vapor Deposition were tested, respectively, which were analyzed according to double-parameter Weibull distribution. Various techniques including XRD and SEM were also used to study the phase composition and microstructure of SiC filament. The result shows that carbon coating plays a very important role on increasing the tensile strength.
Authors: Xin Gui Zhou, Chang Cheng Zhou, Chang Rui Zhang, Ying Bin Cao, Shi Qin Zou
Abstract: 3D braided carbon fiber reinforced silicon carbide (3D-Cf/SiC) composites were fabricated by precursor infiltration and pyrolysis(PIP), with carbon coatings prepared by chemical vapor deposition (CVD) before PIP. The effect of 1873K heat treatment on the mechanical properties of Cf/SiC composites were investigated. The results showed that heat treatment before PIP can increase the density of composites and lead to excellent properties of Cf/SiC composites. The flexual strength of the Cf/SiC composites with one cycle of 1873 K heat treatment reached 571 MPa, shear strength 51 MPa, and fracture toughness 18 MPa⋅m1/2.
Authors: Ai Fang Liu, Zhou Lan Yin
Abstract: Li3V2(PO4)3/C with monoclinic structure were prepared respectively by V2O5 and low valence vanadium oxide V2O3 via solid state reaction. The structure, particle size and morphology of the powders were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed the pure phase Li3V2(PO4)3 with the highest performance can be synthesized at 750 degree by using V2O3 vanadium source. The capacity retention had nearly 100% after 40-cycles at 0.5 C. It has relative capacity retention and higher specific capacity, comparing with V2O5 vanadium source at the optimal synthesis temperature. The electrochemical impedance spectra (EIS) manifests the capacity degradation was mainly caused by the increased solution impedance and electrochemical impedance.
Authors: Chang Su Kim, Soon Ki Jeong
Abstract: The electrochemical properties of carbon-coated FeS2 were investigated as a positive electrode material for lithium secondary batteries. The carbon-coated FeS2 powders were synthesized by ball-milling using polyaniline as the carbon source. The particles in the carbon-coated FeS2 samples were smaller than those in the pristine FeS2 samples. The electrochemical performance, including capacity, of these batteries was improved by carbon-coating by ball-milling. However, the initial coulombic efficiency decreased because of the reduction of the oxidized products on FeS2 surface. The reduction in particle size provides a larger contact area for the electrolyte. Larger quantities of oxidation products were formed by the reduction of FeS2 in the presence of air and water after carbon-coating. Therefore, the poor initial coulombic efficiencies of carbon-coated FeS2 electrodes were caused by the reduction of the oxidized products on the FeS2 surface.
Authors: Chang Su Kim, Yong Hoon Cho, Kyoung Soo Park, Soon Ki Jeong, Yang Soo Kim
Abstract: We investigated the electrochemical properties of carbon-coated niobium dioxide (NbO2) as a negative electrode material for lithium-ion batteries. Carbon-coated NbO2 powders were synthesized by ball-milling using carbon nanotubes as the carbon source. The carbon-coated NbO2 samples were of smaller particle size compared to the pristine NbO2 samples. The carbon layers were coated non-uniformly on the NbO2 surface. The X-ray diffraction patterns confirmed that the inter-layer distances increased after carbon coating by ball-milling. This lead to decreased charge-transfer resistance, confirmed by electrochemical impedance spectroscopy, allowing electrons and lithium-ions to quickly transfer between the active material and electrolyte. Electrochemical performance, including capacity and initial coulombic efficiency, was therefore improved by carbon coating by ball-milling.
Authors: Chang Sam Kim, Sung Ik Hwang, Shin Woo Kim
Abstract: The electrochemical properties of LiFePO4 as a cathode of lithium ion batteries considerably depend on a particle size of LiFePO4 and a condition of carbon coating. In this study, LiFePO4 powders were prepared using ultrasonic spray pyrolysis method, and then LiFePO4/C composites were made by infiltrating sucrose solution into LiFePO4 powders, drying, high-energy milling and annealing. The effects of high-energy milling were analyzed by comparing with electrochemical properties of powders synthesized without high-energy milling. It was found that the milling process drastically reduced the particle size of synthesized powders and electrical conductivity, and improved discharge capacity, cycle stability and rate performance.
Authors: Li Wang, Yu Shan, Guang Chuan Liang, Xiu Qin Ou, Guang Chao Yu
Abstract: Phase pure Li4Ti5O12/C composite was synthesized by solid-state method using Li2CO3 and anatase TiO2 as starting materials, and glucose, citric acid and oxalic acid as carbon sources, respectively. The effects of different carbon sources and various glucose amounts on the microstructure and electrochemical properties were systematically investigated. The as-prepared samples were characterized by means of XRD, SEM and particle size analysis. The electrochemical properties were investigated in terms of constant-current charge/discharge cycling tests. The results showed that the Li4Ti5O12/C composite with 2wt% glucose exhibited the optimal electrochemical performance with a specific discharge capacity of 190.8mAh/g at 0.2C rate. The discharge capacity could still reach 151.0mAh/g after 80 cycles at 1C rate, exhibiting excellent cycling performance.
Authors: Jing Zhu, Yong Guang Liu, Qing Qing Tian, Ling Wang, Ji Lin Cao
Abstract: Li0.95Na0.05Ti2(PO4)3/C nanocomposite was prepared by sol-gel method.The structure and morphology of the samples were characterized by XRD, SEM which showed the particles had typical NASICON structure and diameter range from 400~500nm. The electrochemical performance were tested by cyclic voltammetry and galvanostatic charge–discharge. Results show Li0.95Na0.05Ti2(PO4)3/C nanocomposite exhibitsmuch better electrochemical performance than bare Li0.95Na0.05Ti2(PO4)3.
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