Papers by Author: Keigo Sato

Abstract: The electrochemical properties of titanate nanosheets and layer-structured lithium titanate obtained by restacking of titanate nanosheets were investigated in comparison with those of layer-structured lithium titanate obtained by ion-exchange. Restacked lithium titanate was synthesized by reassembling titanate nanosheets with LiOH aqueous solution. The nanosheets were 50-200 nm wide and 1.7 nm thick. The crystal structure inside the nanosheets was the same as that the of parent material. The oxidation current peaks observed in cyclic voltammograms of titanate nanosheets and restacked material were 1.6 V (Li/Li+), which was lower than that of ion-exchanged material by 0.3 V. The discharge capacity of restacked material was 96 mAh g-1, indicating that 32% of the titanium ions were reduced.

Abstract: High-rate lithium intercalation properties of the Li-Mn-oxide synthesized by the reassembly of MnO2 nanosheets were examined. The colloidal suspension of MnO2 nanosheets was prepared by the exfoliation of proton-exchanged form of layered manganese oxide through the reaction with tetrabutylammonium hydroxide aqueous solution. The results of chemical analysis indicated that a Li-Mn-oxide had a chemical formula of Li0.31MnO2·0.05H2O. The discharge capacity of a Li-Mn-Oxide was 193 mAh/g initially, and decreased gradually during cycling. A Li-Mn-oxide exhibited the discharge capacity of 79 mAh/g at the current density of 2 A/g, and it was 52 % of 151 mAh/g at the current density of 50 mA/g.