Papers by Author: Hideyuki Morimoto

Abstract: Amorphous fine powder in the Li2O-Al2O3-TiO2-P2O5 (LATP) system were prepared directly from a mixture of Li2O, Al2O3, TiO2, and P2O5 as starting materials using a mechanical milling technique at room temperature. LATP glass-ceramics were obtained by heat treatment of the mechanochemically prepared amorphous powder over the crystallization temperature. X-ray diffraction peaks due to LiTi2(PO4)3 and AlPO4 crystals for LATP glass-ceramics were observed. Thus, high lithium ion conducting LATP glass-ceramics solid electrolytes were prepared successfully from the mechanochemically prepared amorphous powder. The LATP glass-ceramic fine particles were investigated as coating materials of LiCoO2 cathode in lithium ion batteries. The LATP glass-ceramics coated LiCoO2 electrode materials exhibited a good charge-discharge performance for charging up to a high voltage (4.5 V vs. Li/Li+).

Abstract: Composite electrode materials of amorphous FeOOH-based particles and carbon powder were prepared by heat treatment of composite powder obtained by hydrolyzing of mixed aqueous solutions of FeCl3 and Ti(SO4)2 into which electron conducting carbon powder was dispersed. They exhibited high capacities over 150 mAh g-1 and good cycle performance at large charge-discharge current density of 5 mA cm-2 (ca. 1 A g-1). In this case, the heat treatment was effective process to improve the cycle performance.

Abstract: Anatase-type TiO2-based oxide gel /carbon composites were treated chemically with LiOH aqueous solution at 60 °C. The crystalline phase of treated powder was examined by powder x-ray diffraction using CuKα radiation. The main diffraction peaks may be detected as belonging to cubic LiTiO2. High-rate lithium intercalation properties of the samples were estimated in nonaqueous electrolyte including lithium ions. The composite electrodes exhibited high coulombic efficiency over 90% at first cycle and high capacities over 200 mAh g-1 after 200 cycle at large charge-discharge current density of 5.0 mA cm-2 (3.7 A g-1). The composite materials are one of the promising candidates as electrode materials for energy storage devices, such as hybrid capacitor, that require high-power operations.

Abstract: Composite materials of β-FeOOH particles and carbon powder were prepared by hydrolyzing of FeCl3+Ti(SO4)2 (aq.) in which carbon powder was dispersed. β-FeOOH formed in the presence of Ti(IV) ions became amorphous and/or low crystallinity. The composite materials prepared in the presence of Ti(IV) ions worked as lithium intercalation electrodes in nonaqueous electrolytes including lithium ions. The electrodes exhibited a good cycle performance at large charge-discharge current density over 5 mA cm-2 ( 4 A g-1 per weight of active material). The composite materials are one of the promising candidates as electrode materials for energy storage devices, such as hybrid electrochemical supercapacitor, that require high-power operations.

Abstract: Composite electrode material of crystalline b-FeOOH and carbon was prepared by hydrolyzing of FeCl3 (aq.) in which carbon powder with various specific surface areas was dispersed. Composite electrode material of b-FeOOH fine particles and Ketjen black (KB:specific surface area 1270 m2 g-1) of high specific surface area exhibited the high capacity over 250 mAh g-1 per b-FeOOH weight and good cycle performances at rapid charge-discharge current density over 5 mA cm-2 (ca. 5.0 A g-1 per b-FeOOH weight) in nonaqueous electrolytes including lithium ions. Composite electrode materials of crystalline b-FeOOH and carbon are one of the promising candidates as electrode materials for energy storage devices that high-power operations are required.