Takayuki Kodera

Powder Characterization and Electrochemical Properties of LiNi0.5Mn1.5O4 Cathode Materials Produced by Large Spray Pyrolysis Using Flame Combustion

LiNi0.5Mn1.5O4 cathode materials were produced by spray pyrolysis apparatus using the flame combustion. SEM revealed that as-prepared powders had spherical morphology with porous microstructure which had an average diameter of about 2 μm with broad size distribution. After the calcination, LiNi0.5Mn1.5O4 powders with polygonal morphology and narrow particle size distribution were obtained. XRD showed that LiNi0.5Mn1.5O4 was well crystallized after the calcination at 900°C. Rechargeable measurement of LiNi0.5Mn1.5O4 cathode showed that the long plateau was observed at 4.7 V in discharge curve of LiNi0.5Mn1.5O4 cathode and its discharge capacity was 145 mAh/g at 1 C. The capacity retention of LiNi0.5Mn1.5O4 cathode were 95% at 1 C after 100 cycles. The discharge capacity and capacity retention of LiNi0.5Mn1.5O4 cathode were 125 mAh/g and 88% at 20 C. LiNi0.5Mn1.5O4 cathode exhibited also stable cycle performance at 50∘C.

Mass Production of LiFeP/C Powders by Large Type Spray Pyrolysis Apparatus and Its Application to Cathode for Lithium Ion Battery

Spherical LiFeP/C powders were successfully produced at a rate of 100 g/h using a large type spray pyrolysis apparatus. Organic compounds such as citric acid and sucrose were used as carbon sources. Scanning electron microscopy observation showed that they had a spherical morphology with nonaggregation. X-ray diffraction analysis revealed that the olivine phase was obtained by heating at under argon (95%)/hydrogen (5%) atmosphere. The chemical composition of LiFeP/C powders was in good agreement with that of the starting solution. Electrochemical measurement revealed that the use of citric acid was most effective in ensuring a high rechargeable capacity and cycle stability. The rechargeable capacity of the LiFeP/C cathode obtained using citric acid was 155 mAh/g at a discharge rate of 1 C. Because of the good discharge capacity of the LiFeP/C cathode, it exhibited excellent cycle stability after 100 cycles at each discharge rate. Moreover, this high cycle stability of the LiFeP/C cathode was maintained even at .

Synthesis of Li2Ti3O7 Anode Materials by Ultrasonic Spray Pyrolysis and Their Electrochemical Properties

Ramsdellite-type lithium titanate (Li2Ti3O7) powders were synthesized by performing ultrasonic spray pyrolysis, and their chemical and physical properties were characterized by performing Scanning Electron Microscope (SEM), powder X-ray Diffraction (XRD), and Inductively Coupled Plasma (ICP) analyses. The as-prepared Li2Ti3O7 precursor powders had spherical morphologies with hollow microstructures, but an irregularly shaped morphology was obtained after calcination above 900 °C. The ramsdellite Li2Ti3O7 crystal phase was obtained after the calcination at 1100 °C under an argon/hydrogen atmosphere. The first rechargeable capacity of the Li2Ti3O7 anode material was 168 mAh/g at 0.1 C and 82 mAh/g at 20 C, and the discharge capacity retention ratio was 99% at 1 C after the 500th cycle. The cycle performance of the Li2Ti3O7 anode was also highly stable at 50 °C, demonstrating the superiority of Li2Ti3O7 anode materials reported previously.

Mass Production and Battery Properties of LiNi0.5Mn1.5O4 Powders Prepared by Internal Combustion Type Spray Pyrolysis

Internal combustion type spray pyrolysis apparatus was used to prepare cathode materials for lithium ion batteries. Spherical LiNi0.5Mn1.5O4 precursor powders with an average size of about 2 m were successfully produced by this technique. After calcination at 800°C, LiNi0.5Mn1.5O4 precursor powders crystallized to a spinel structure. The spherical morphology changed to an irregular morphology at temperatures higher than 900°C. The discharge capacity of the LiNi0.5Mn1.5O4 cathode was 130 mAh/g at 1C. After 300 cycles at 1C, 90% of the initial discharge capacity was maintained, and after 100 cycles at 6C, 70% of the discharge capacity at 1C was maintained.

Synthesis and Electrical Properties of La Doped SrTiO3 Powders by Ultrasonic Spray Pyrolysis

La-doped SrTiO3 (LST) powders were synthesized by ultrasonic spray pyrolysis using an aqueous solution of a metal nitrate. SEM images showed that the as-prepared LST powders had a spherical morphology with a diameter of 1 μm. XRD patterns showed that the crystal phase of the as-prepared powders was amorphous and that the powders crystallized to the perovskite phase by calcination at 900 °C. The sintered LST body had the highest electrical conductivity at a La doping concentration (Lax) of 0.1 under a reducing atmosphere. A solid oxide fuel cell (SOFC) with La0.1Sr0.9TiO3Sm-doped CeO2 (1:9) as the anode exhibited a maximum power density of 137.8 mW/cm2 and an open circuit voltage of 1.08 V at 880 °C.

Synthesis and Lithium Battery Properties of LiM(M=Fe,Al,Mg)xMn2-xO4 Powders by Spray Pyrolysis

LiM(M=Fe,Al,Mg)XMn2-XO4 fine powders were synthesized by the ultrasonic spray pyrolysis using metal nitrate solution. LiMn2O4 powders obtained by this method have a spherical morphology with a submicron size. XRD revealed that as-prepared powders were crystallized to spinel structure with Fd3m space group. LiM(M=Fe,Al,Mg)XMn2-XO4 showed enhanced cycling performance at room temperature. Reduced Jahn-Teller distortion of LiMn2O4 by metal doping was responsible for enhanced cycle performance of LiMn2O4.

Synthesis and Characterization of BaTiO3 Nano-Particle by Aerosol Plasma Pyrolysis Process

Homogeneous BaTiO3 nano-sized powders were successfully prepared by spray pyrolysis using multiphase plasma under the air atmosphere. Particle size, morphology, crystal phase and crystallinity of as-prepared powders were characterized by SEM and XRD. The effect of starting precursor solution on the formation of nanoparticles was investigated. The use of Ba/Ti aqueous solution derived from malic acid led to formation of cubic BaTiO3 nanoparticles with 50 nm size.

Preparation and Electrochemical Properties of LiMnPO4 Nanoparticles by Polyol Method

Plate-like LiMnPO4 particles were prepared by polyol method. The chemical and physical properties of plate-like LiMnPO4 particles were characterized by XRD and SEM. The thickness of plate-like LiMnPO4 particles was approximately 35 nm. XRD pattern of plate-like LiMnPO4 was good agreement with orthorhombic olivine structure. The first discharge capacity of C/LiMnPO4 cathode was approximately 95 mAh/g. 99.9 % of initial discharge capacity was maintained after 100 cycles.

Synthesis of Carbons Added LiFePO4 Powders by Two-Fluid Nozzle Spray Pyrolysis and Measurement the Charge-Discharge Properties

LiFePO4/C powders were synthesized by ultrasonic spray pyrolysis using carbon powder instead of organic substances as the carbon source. LiFePO4 (LFP) powders containing different types of carbon powders were prepared and used as cathode active materials in lithium ion batteries. The charge-discharge properties of lithium ion batteries with LFP, LFP/AB, and LFP/CNT powders as the cathode material were worse than those of the battery with LFP/sucrose powder as the cathode active material.

Characterization of Samarium Doped Ceria Powders having High Specific Surface Area Synthesized by Carbon-assisted Spray Pyrolysis

Spherical samarium doped ceria (Ce0.8Sm0.2O1.9, SDC) powders having high specific surface area (SSA) were successfully synthesized by carbon-assisted spray pyrolysis (CASP). Saccharides, such as monosaccharides and disaccharides, or organic acids were used as carbon sources. The physical and chemical properties of these powders were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Thermo gravimetry-Differential Thermal Analysis (TG-DTA), and BET. Decarbonized powders obtained by this method exhibit spherical morphologies and nano- and submicron-sizes. The SSA of SDC obtained from CASP was more than seven times higher than that obtained from conventional spray pyrolysis (CSP). The SSA of the decarbonized SDC powders obtained by calcination at 900 °C was estimated to be approximately 70 m2/g by using the BET method. The relative density of SDC obtained from CASP was higher than that obtained from CSP. The relative density of the SDC pellet was highest (96 %) when it was sintered at 1400 °C.