Papers by Keyword: Anode

Abstract: The anodic aluminum oxide template was prepared and used to fabricate polyacrylonitrile (PAN) nanowire arrays by mechanical hydraulic method, which provides a new idea for the preparation of polymer nanowires. By further carbonize the PAN nanowires at elevated temperatures, the porous nitrogen-rich carbon nanowires could be directly obtained and used as lithium-ion batteries anode material. The nitrogen-rich carbon nanowire based anode exhibited high initial capacities and maintained an outstanding reversible lithium storage capacity of 317.12 mAh g^-1 after 50 cycles at a current density of 30 mA g^-1, combined with an excellent rate capability of 317.17, 296.70, 265.02, 234.71, 177.02 mAh g^-1 under the current density of 30, 50, 100, 200, 500 mA g^-1 respectively. Further, this nitrogen-rich carbon nanowire material also has unique advantages in catalysis, supercapacitors and hydrogen storage application potential due to the porous carbon nanowire structure and the large amount of nitrogen doping.

Abstract: Nanosized spinel Li4Ti5O12 was successfully synthesized by a solid state reaction method at 800°C according to the Li₄Ti₅O₁₂ cubic spinel phase structure. In this synthesizing process, anatase TiO₂ and Li₂CO₃ were used as reactants. The average grain size of the synthesized powders was around 200 nm. The synthesized Li₄Ti₅O₁₂ powder was characterized X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectrometry (EDS), and Specific Surface Area Analyzer (BET, Brunner-Emmett-Teller) respectively. X-ray diffraction results show that calcination temperature and time have the important effects on the crystal structure of Li₄Ti₅O₁₂ powder. In this study, we used a first principle method, based on the density functional theory to explore electronic and structural properties of Li₄Ti₅O₁₂, as anode material for lithium ion batteries. Differences on these properties between delithiation state Li₄Ti₅O₁₂ and lithiation state Li₇Ti₅O₁₂ are compared. All the predicted structural and electrochemical properties agree closely with the experimental findings in literature. The average intercalation voltage of 1.4V during charging/discharging were obtained. We have shown that the Li₄Ti₅O₁₂ material exhibits insulating behavior with the band gap of 3.16 and 3.90 eV using the GGA and GGA+U+J₀ calculations respectively. Li₇Ti₅O₁₂ becomes metallic as Li atoms inserted in Li₄Ti₅O₁₂ material. Spinel Li₄Ti₅O₁₂ has been regarded as an attractive anode material for the development of high-power lithium-ion batteries because of its unique attributes of high safety and rate capability.

Abstract: Development of Molten Carbonate Fuel Cells is strongly governed by improvement of durability and efficiency of the main components. This can only be achieved by defining the relationships between structure and properties of materials for MCFC. Present work introduces the results of optimization of the manufacturing process parameters and characterization of materials obtained herewith. Tape-casting manufacturing technique based on forming of a slurry with strictly defined composition and properties was used. The influence of slurry composition and further heat treatment conditions are correlated with structural parameters such as porosity and pore morphology in final products.

Abstract: Perovskite La_1-xSr_xFe_0.7Ni_0.3O_3-δ with x = 0.0, 0.1 &0.2 denoted LSFN_x has been investigated as potential symmetrical electrode in solid fuel cells (SOFCs). The crystal structure is in pure orthorhombic phase for x = 0.0, orthorhombic-cubic phase coexist for x = 0.1 and pure cubic phase for x = 0.2. Structural properties are studied by X-ray powder diffraction (XRPD), refined by Rietveld analysis. SEM images show the morphology of as prepared and calcined samples either the compatibility between those electrodes and LSGM electrolyte in presence of 50% wt of Ce_0.8Gd_0.2O_2-δ, so that, lower chemical reactivity was found. Total conductivity, impedance in high, medium and low frequencies HF, MF and LF respectively, and resistance polarization (Rp) are determined in air. LaFe_0.7Ni_0.3O_3-δ has a good response in all ranges of frequencies but La_0.9Sr_0.1Fe_0.7Ni_0.3O_3-δ and La_0.8Sr_0.2Fe_0.7Ni_0.3O_3-δ have response only in HF and MF and exhibit Rp values as low as LaFe_0.7Ni_0.3O_3-δ .

Abstract: A facile two-step method for preparation of porous carbon materials was reported. We used a novel Co-MOF, made by cobalt nitrate and two organic ligands (9-ethylcarbazole-3,6-dicarboxylic acid and 1,3,5-Benzenetricarboxylic acid), as the template to synthesize the porous carbon through high temperature carbonization, which was applied as an anode material for lithium-ion batteries. A reversible capacity was maintained as high as 549 mA h g^-1 after 49 cycles at a current density of 100 mA g-1, with coulombic efficiency of over 95%. The prepared porous carbon electrode also exhibited superior cycle stability and rate performance, making it a promising anode material for lithium-ion batteries.

Abstract: The anode microstructure is crucial for the performance of solid oxide fuel cell(SOFC). The porous anode with high porosity and long cylindrical pores was prepared by using cotton-fiber as pore-former. With Ni-yttria stabilized zirconia (YSZ) as anode, La_0.85Sr_0.15MnO₃-YSZ as cathode, YSZ electrolyte-supported cell was fabricated by slurry coating method. For a comparison, the unit cell with the conventional flour as anode pore former was prepared. All the as-prepared cells were measured in hydrogen at 650 to 800 °C. The microstructure of tested cells was observed by scanning electron microscopy (SEM). The SEM shows that the long cylindrical pores produced by cotton-fibers were beneficial to provide continuous gas pathways for rapid diffusion of fuel and reaction products in the anode. Compared the flour of 373.74 mW·cm^-2 at 800 °C, the maximum density of unit-cell prepared by cotton-fibers was higher than 900 mW·cm^-2, which was attribute to an enlarger active reaction sites created by cotton-fibers for hydrogen oxidation.

Abstract: By localized impedance spectroscopy (LEIS) and electrochemical impedance spectroscopy (EIS), the effect of loading potential variation on the performance of direct methanol fuel cell ( DMFC ) anode was studied. During surface scanning, the local impedance of the anode showed sawtooth-like distribution under potential loading, which meant the electrochemical activity in the anode surface was nonuniform. Meanwhile, the local impedance tended to increase with loading potential increasing. After loading 16h and 72h at 0.6V, the average size of catalysts changed from 3.4nm to 3.6nm and 4.4nm, increased by 5.88% and 29.41%. After loaded for 72h under 0.8V, the ratio of Pt:Ru in catalyst changes from 2:1 to 3.9:1. It is the change of the difference in local area, which showed impedance increase, catalyst particle size growing up and agglomeration, the loss of Ru, that contributed to the performance decay of DMFC anode.

Abstract: nanoSi-C composite was prepared using eletronspinning technique. The microstructure and morphology of the Si-C composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performances of the Si-C composite were tested by battery testing system. The results showed that the Si-C composite not only behaved high initial capacity but also good cycle performances. The reversible discharge capacity could remain at 860 mAhg^-1 when current density was 50 mAg^-1. The rate reversible capacity is much higher than that of pure nanoSi anode at same condition.

Abstract: The characteristics of the starting powder in powder preparation method are important for enhancement of cell performance. In this study, the composite anode powders of NiO–samarium-doped ceria carbonates (SDCC) were prepared by using different NiO loadings (50–70 wt.%) via high-energy ball milling. The composite anode powders were ball-milled in ethanol at a milling speed of 550 rpm. The obtained NiO–SDCC composite anode powders were characterized by XRD, FTIR, FESEM, and EDS. Results indicate that the composite anode powders demonstrated good chemical compatibility between NiO and SDCC, given that no new phases were detected in the XRD analysis. FTIR spectra confirmed that the composite anode powders contain carbonates in amorphous state after high-energy ball milling. FESEM investigation revealed well-distributed fine particles and significant reduction of particle size at nanoscale compared with the powder prepared using NiO particles as the starting material. EDS mapping verified the homogeneity of the composite powder with good elemental distribution. Thus, high-energy ball milling is an effective method to prepare NiO–SDCC composite anode powders within a relatively short processing time.

Abstract: A new concept for synthesis of the nanostructured transition metal oxides had been proposed. In particular, the method of pulsed high-voltage discharge was adopted for synthesis of α-MoO₃ nanostructure with orthorhombic crystal lattice. The as-prepared α-MoO₃ was investigated as anode for Li-ion battery. The 30-fold charge–discharge cycling has shown that material specific capacity (approximately 90 mAh g^–1) is not high, however excellent reversibility was achieved (the Coulombic efficiency equals to 99.9%). Thus the method opens new ways for the synthesis of nanomaterials with stable reversible capacities for Li-ion batteries.