A Novel Layered Titanoniobate LiTiNbO5: Topotactic Synthesis and Electrochemistry versus Lithium.

A new layered titanoniobate, LiTiNbO5, an n = 2 member of the AxM2nO4n+2 family, has been synthesized using a molten salt reaction between HTiNbO5 and an eutectic “LiOH/LiNO3”. This compound crystallizes in the P21/m space group with a = 6.41 A, b = 3.77 A, c = 8.08 A, and β = 92°. It exhibits |TiNbO5|∞ layers similar to HTiNbO5, but differs from the latter by a “parallel configuration” of its |TiNbO6|∞ ribbons between the two successive layers. The topotactic character of the reaction suggests that exfoliation plays a prominent role in the synthesis of this new form. This new phase intercalates reversibly 0.8 lithium through a first-order transformation leading to a capacity of 94 mAh/g at a potential of 1.67 V vs Li/Li+.