Abstract
A layer structured titanate Cs2Ti5O11·(1 + x)H2O (x = 0.70) has been prepared in a solid state reaction using Cs2CO3 and anatase type TiO2 at 900°C. Ion exchange reactions of Cs+ in the interlayer space were studied in aqueous solutions. The single phases of Li+, Na+ and H+ exchange products were obtained. The three kinds of resulting titanates were evaluated for use as the cathodes in rechargeable sodium batteries after dehydrations by heating at 200°C in a vacuum. The electrochemical measurements showed that they exhibited the reversible Na+ intercalation-deintercalation in a voltage range of 0.5 - 3.5 V or 0.7 - 4.0 V. The Li+ exchange product showed the best performance of the discharge-charge capacities in this study. The initial Na+ intercalation-deintercalation capacities of the Li2Ti5O11 were 120 mAh/g and 100 mAh/g; the amounts of Na+ correspond to 1.9 and 1.6 of the formula unit, respectively. The titanates are nontoxic, inexpensive and environmentally benign.
Highlights
Sodium ion batteries have emerged for the ideal alternative to the lithium ion batteries which have the problems of lithium availability and cost
We have studied the characterizations of layer structured titanates and Niobate [1]-[8] for the cathodes of lithium ion batteries
We found that novel cathode materials for sodiumion batteries derived by ion exchange reactions from a layered titanate of Cs2Ti5O11·(1 + x)H2O
Summary
Sodium ion batteries have emerged for the ideal alternative to the lithium ion batteries which have the problems of lithium availability and cost. We have studied the characterizations of layer structured titanates and Niobate [1]-[8] for the cathodes of lithium ion batteries. We found that novel cathode materials for sodiumion batteries derived by ion exchange reactions from a layered titanate of Cs2Ti5O11·(1 + x)H2O. The framework is built up by five TiO6 octahedra sharing edges. These unites are joined to the same block sharing edges to form zig-zag layers and sharing corners staggered sheets forming [Ti5O11]2− layers. The titanate Cs2Ti5O11 intends to contain water molecules in the interlayer space with Cs+ from the air at room temperature forming Cs2Ti5O11·(1 + x)H2O (0.5 < x < 1)
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