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.