Papers by Keyword: Lithium Ion Secondary Battery

Abstract: ron fluoride (III) anhydrate fine particle was prepared by drying in vacuum from FeF₃·3H₂O, a mechanical milling process and a calcination at 473 773 K. Particle size of FeF₃·3H₂O was ca. 3 5 μm and that of FeF₃ anhydrate was 100 500 nm after drying and milling. FeF₃ sample only after drying and milling was hygroscopic and became FeF₃·3H₂O under atmosphere. FeF₃ became stable under atmosphere after oxidation at 673 K for more than 20 minutes. It was found that Fe₂O₃ was produced by calcination and covered the surface of FeF₃ particles. In Charge-discharge measurements, the discharge capacity of these FeF₃ samples was 150 - 200 mAh/g at a discharge rate of 0.1 C. The oxidation could improve the discharge properties of FeF₃ cathode.

Abstract: Effects of lattice defects on cathode properties of LiMn2O4 synthesized at low temperatures were investigated. LiMn2O4 powders were synthesized by a sol-gel method. The specific capacities of LiMn2O4 decreased from 134 to 81 mAh g-1 with decreasing heating temperature from 750 to 200°C. X-ray absorption spectroscopy showed that a large amount of lattice defects such as cation vacancies existed and cation mixing occurred in LiMn2O4 calcined at low temperatures. It was found that the low specific capacities of LiMn2O4 calcined at low temperatures were attributed to these lattice defects.

Abstract: Lithium intercalation properties were investigated for mesoporous titania, prepared by hydrolysis of titanium tetrabutoxide followed by calcining at various temperatures. X-ray diffraction analysis showed that synthesized titania were anatase phase. The B.E.T. surface area of mesoporous titania decreased with increasing calcining temperature, but that of mesoporous titania calcined at 450°C was over 50 m2/g. Lithium intercalation capacities of mesoporous anatase increased with increasing calcining temperature up to 450°C. Mesoporous anatase titania calcined at 450°C showed a capacity of 118 mAh/g at a current density of 1 A/g. The lithium intercalation properties depended on crystallinity, remaining water content and mesopore size.

Abstract: Lithium intercalation properties of octatitanates composed of nanosheets were examined. Several types of nanosheet-octatitanates were prepared by the reassembly of tetratitanate nanosheets in colloidal suspension, which were separated centrifugally at various revolutions, and then by a heat treatment. The colloidal suspension was obtained by the exfoliation of tetrabutylammonium tetratitanate intercalation compound. The capacities of the octatitanates composed of nanosheets were approximately 160 mAh/g, and they were maintained even after the exfoliation and the reassembly. The octatitanate composed of nanosheets with relatively small dimensions centrifugally separated at 6000 rpm exhibited a large capacity of 140 mAh/g at a relatively high current density of 1 A/g. The nanosheet process was found to be effective in improving the high rate capability.