Key Engineering Materials Vols. 336-338

Abstract: Al2O3-coated LiNi1/3Co1/3Mn1/3O2 powders with excellent electrochemical performance have been synthesized. The electrochemical performance of Al2O3-coated LiNi1/3Co1/3Mn1/3O2 electrodes has been studied as function of the level of Al2O3 coating. Coated LiNi1/3Co1/3Mn1/3O2 samples shows higher discharge capacity and better capacity retention than the base one. Among the coated samples, 1.0mol% coated sample exhibits the best electrical performance. It presents an initial discharge capacity of 174.5 mAh g-1 over 2.5~4.4V, and 84.7% capacity retention after 30 cycles over 2.5~4.6V.

Abstract: Partial oxygen in LiNi0.7Co0.3O2 was replaced by chlorine to form LiNi0.7Co0.3O1.9Cl0.1. Phase structure of LiNi0.7Co0.3O1.9Cl0.1 was identified as a pure hexagonal lattice of α-NaFeO2 type by X-ray diffraction. Discharge capacity of LiNi0.7Co0.3O1.9Cl0.1 was 202 mAh/g in initial cycle at 15 mA/g current density in 2.5- 4.3 V potential window. The constant current charge/discharge experiments and cyclic voltammograms showed that chlorine addition was effective to improve reversible capacity and cycle stability of LiNi0.7Co0.3O2.

Abstract: LiFePO4/Carbon composite cathode material was prepared by pelleting and subsequent pyrolytic cracking process in N2 atmosphere with carbon source of polyvinyl alcohol (PVA). XRD crystal analysis indicates that single LiFePO4 phase and amorphous carbon can be found in the products. SEM observation shows a special micro-morphology of sample, which is favorable for enhancement of electrochemical properties. The discharge capacity of the LiFePO4/C composite was 135 mAh/g, close to the charge capacity of 153 mAh/g at low rate of 0.1C. At 0.2C, the specific capacity was about 117.4 mAh/g, which is satisfied for power source of Electric Vehicle for its flat discharge platform.

Abstract: Mn/Pb composite oxides were prepared by solid-state reaction by KMnO4 with manganese acetate and lead acetate at low temperature. The products were characterized by XRD and TEM. The results show that the composite oxides are nano-size and amorphous structure. Electrochemical characterizations were performed by cyclic voltammetry (CV) and constant current charge-discharge in a three-electrode system. The potential windows of Mn/Pb composite oxides electrode are increased. With increasing the ratio of Pb, the specific capacitance goes through a maximum at 20% mol Pb. The specific capacitance of pure MnO2 is 158 F/g and is improved to 180 F/g for the Mn0.8Pb0.2Ox composite oxide by constant current discharge.

Abstract: In this paper, firstly, titanate nanotubes was synthesized by hydrothermal method with commercial antase-type TiO2 powder as the raw material. TiO2 nanotubes (TNTs) can be obtained by heat-treating the as-prepared titanate nanotubes at 400 °C. Secondly, an electrode with 30 % TNTs and 70% nanocrystalline TiO2 was designed and prepared successfully. By using the nano-electrode as the photoanode of DSC, the light-to-energy conversion efficiency of 5.42 % was obtained. In addition, the effect of hydrothermal temperature on the crystal growth of nanotubes and the effect of tert-butyl pyridine (TBP) on the photoelectric performance of the DSC were also discussed.

Abstract: A novel process was proposed for preparing spinel LiMn2O4 with spherical particles from cheap materials of MnSO4, NaOH, NH3•H2O and LiOH. Its successful preparation started with a carefully controlled crystallization of Mn3O4, leading to the spherical shape of its particles and a high tap density. The mixture of Mn3O4 and LiOH was sintered to produce LiMn2O4 with spherical particle size retention. The spherical particles of spinel LiMn2O4 were of excellent fluidity and dispersivity, and had tap density as high as 2.14 g cm-3 and the initial discharge capacity reaching 128 mAh g-1. Its 15th cycle capacity kept to be 125 mAh g-1.

Abstract: A concept for quantitative design of sealing glasses was proposed for planar solid oxide fuel cells (SOFC) applications, by which chemical and physical compatibility of a glass with other materials can be predicted through simulation based on a thermodynamic model and a combined model. Using this method, a sealing glass was successfully developed. The thermal expansion coefficient (TEC) of the glass was determined to be 9.9×10-6 K-1 (room temperature to 631°C), which is very close to the value of 10.0 × 10-6 K-1 measured for 8YSZ. Investigations revealed that the sealing glass had very good thermal stability, where the change of the TEC value was within the range of equipment error. The glass was also proved to be chemically compatible with 8YSZ, by the fact that no obvious interfacial reaction was detected after being heat-treated with 8YSZ at 700°C for 500 h.

Abstract: A single cell with a two-layer electrolyte consisting of an yttria stabilized zirconia (YSZ, Y2O3 8 mol%) layer and an Sm-doped ceria (SDC, Sm2O3 20mol%) interlayer has been fabricated on porous YSZ-NiO anode support. The layer of YSZ electrolyte was prepared by modified electrostatic powder coating method and the SDC interlayer by screen-printed method on the green YSZ layer. After co-firing at 1400°C for 5 h, the two-layer film with a dense YSZ film of about 15μm and porous SDC film of about 25μm was fabricated. The performances of as-fabricated single cell using La0.8Sr0.2FeO3 as cathode were tested using H2-3% H2O as fuel and air as oxidant at 800°C. Results indicated that the peak power density of a single cell with SDC interlayer reaches 469 mW/cm2 at 800°C, obviously higher than that of without SDC interlayer, which is about 300 mW/cm2 at 800°C.

Abstract: Low temperature (300 to 650 °C) ceramic fuel cells (LTCFCs) were developed by using novel AC-MO-CSC anode material based on activated carbon (AC), transition metal oxides (MO) and ceria-salt composites (CSC). The activated carbon was first used to improve the characters of anode materials, especially to enhance the anode catalytic activity for liquid hydrocarbon fuels, e.g., methanol. The microstructure, conductivity and electrochemical properties of anode materials were investigated as functions of the activated carbon. Using the anode materials, maximum power density of 0.2 W cm-2 was achieved for fuel cells directly operating methanol at 600 °C.