Papers by Author: Izumi Mukoyama

Abstract: LiNi1/3Co1/3Mn1/3O2 precursor powders were successfully prepared by internal combustion type spray pyrolysis. The production capacity of precursor powders was about 1 kg/h when the solution concentration was 0.5 mol/dm3. Particle size, morphology and crystal phase of LiNi1/3Co1/3Mn1/3O2 powders were characterized by XRD and SEM. XRD showed that a layered rock salt structure with a R3m space group was formed by calcination at 750 °C for 10 h. SEM showed that hollow powders with a particle size of 6 μm and irregular morphology were obtained. The discharge capacity of LiNi1/3Co1/3Mn1/3O2 was 130 mAh/g, which showed good cycle performance.

Abstract: 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.

Abstract: Carbon doped LiFePO4 precursor particles were successfully prepared by spray pyrolysis. The saccharides such as monosaccharide and disaccharide or organic acid were used as carbon source. SEM observation showed that as-prepared particles had spherical morphology with narrow size distribution. XRD analysis revealed that olivine phase was obtained by heating at 700°C under the atmosphere of argon/hydrogen (5%). Electrochemical measurement revealed that the discharge capacity of LiFePO4 was improved by the addition of carbon. The addition of citric acid was most effective for the stabilization of cycle life.

Abstract: Spherical LiNi0.5Mn1.5O4 powders were prepared by internal combustion type spray pyrolysis apparatus using gas burner. The powder production capacity was 1 kg/h by this equipment. After calcinations of as-prepared powders contained Ni at different temperatures from 800 to 1200 °C in air for 10h, LiNi0.5Mn1.5O4 powders were obtained. As-prepared particles have a porous microstructure with an average diameter of about 5 μm with narrow size distribution. XRD showed that LiNi0.5Mn1.5O4 powders were well crystallized to a spinel structure with Fd3m space group. LiNi0.5Mn1.5O4 powders calcined at 1000°C show good cycle performance with after 30 cycles discharge capacity of 112mAh/g and 95% retention after 400 cycles between 3.5 V and 5 V.

Abstract: Spherical LiAlxMn2-xO4 fine powders were continuously produced by Internal Combustion Type Spray Pyrolysis Apparatus Using Gas Burner from metal nitrate precursor solutions. XRD showed
that LiAlxMn2-xO4 powders were well crystallized in a spinel structure with the Fd3m space group. As-prepared powders have a spherical particle shape with a diameter of 2.3 μm. As-prepared samples were calcined at 800
 for 10 h in air. The charge/discharge capacity of LiAlxMn2-xO4 was over 100 mAh/g. A powder production capacity speed of 1 kg/h was attained by this system.

Abstract: 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.