Preparation of Layer Structured Titanates and Application as Cathode Materials in Rechargeable Lithium Batteries

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Ion exchange and intercalation properties of the layer structured titanates have been extensively studied. In a previous study, we showed that the layer structured titanate of Cs_xTi_<2-x/4>O_4 exhibited electrochromism by electrochemical redox reactions. Although it was difficult to charge this cathode in the lithium cell, it sems that it is feasible to use the layer structured titanate for cathode materials of the intercalation (rechargeable) lithium batteries. In this study, the layer structured titanates of Cs_xTi_<2-x/2>Mg_<x/2>O4 (x = 0.70), K_xTi_<2-x>Fe_xO_4(x = 0.80), CsTiNbO_5 and CsTi_2NbO_7 have been prepared in solid state reactions using cesium carbonate, potassium carbonate and metal oxides. Alkali and hydrogen ion exchange reactions of these titanates have been studied in aqueous solutions. The single phases of ion exchange products were obtained from the all titanates. They contained interlayer water and the host layers were retained on the ion exchanges. The interlayer water was removed by heating at 110-180℃ in a vacuum.The ion exchange products of Li_<0.51>H_<0.07>Cs_<0.12>Ti_<1.65>Mg_<0.35>O_4, H_<0.79>K_<0.01>Ti_<1.20>Fe_<0.80>O_4, Cs_<0.10>Li_<0.60>H_<0.30>TiNbO_5 and Cs_<0.06>Li_<0.94>Ti_2NbO_7 were evaluated for their uses as the cathode materials in the intercalation (rechargeable) lithium batteries. The cathodes exhibited discharge and charge capacities of 120 and 110 mAh/g, 107 and 69 mAh/g, 130 and 100 mAh/g, 108, and 80 mAh/g for the first cycle in the voltage range of 1.5 - 4.2 V, respectively. It has been found that the ion exchange derivatives of the layer structured titanates can be promising candidates for the cathode materials of the intercalation (rechargeable) lithium batteries. These cathode materials are nontoxic, inexpensive and environmentally benign. It seems that the aim of this study was achieved.