Synthesis, structure, and electrochemical Li-ion intercalation properties of Li2Ti3O7 with Na2Ti3O7-type layered structure

Li2Ti3O7 with the Na2Ti3O7-type layered structure was prepared from Na2Ti3O7 as a parent compound via ion exchange in molten LiNO3/LiCl at 260-280 deg C. The layered crystal structure of Li2Ti3O7 was determined by Rietveld analysis using the X-ray powder diffraction data. The interlayer distance in Li2Ti3O7 was considerably shorter than that in the parent Na2Ti3O7. The two types of Li atoms were tetrahedrally coordinated by the surrounding oxygen atoms in the interlayer space. The electrochemical measurements showed the reversible Li-ion intercalation and deintercalation reactions in a voltage range of 1.5-2.0V (vs. Li/Li+), respectively. The initial Li-ion intercalation capacity of the present Li2Ti3O7 sample was 147mAh g-1; this value is equivalent to 1.48 electron transfers per formula unit.