A novel layered titanoniobate LiTiNbO5: topotactic synthesis and electrochemistry versus lithium.

A new layered titanoniobate, LiTiNbO5, an n = 2 member of the A(x)M(2n)O(4n+2) family, has been synthesized using a molten salt reaction between HTiNbO5 and an eutectic "LiOH/LiNO3". This compound crystallizes in the P2(1)/m space group with a = 6.41 A, b = 3.77 A, c = 8.08 A, and beta = 92 degrees . It exhibits |TiNbO5|(infinity) layers similar to HTiNbO5, but differs from the latter by a "parallel configuration" of its |TiNbO6|(infinity) 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+.