A₃Ti₅NbO₁₄ (A = H, Li and K) family: ionic exchange, physical and electrochemical properties

A new layered titanoniobate, Li₃Ti₅NbO₁₄, a member of the AM₂O₄ family, has been synthesized using a molten salt reaction between H₃Ti₅NbO₁₄ and an eutectic mixture of LiOH and LiNO₃. This compound crystallizes in the P2₁/m space group with a = 9.273(15) Å, b = 3.788(6) Å, c = 8.871(3) Å, and β = 114.33(1)°, as determined by 3D electron diffraction single crystal analysis. It exhibits [Ti₅NbO₁₄]^3- layers similar to K₃Ti₅NbO₁₄, but differs from the latter by a 'parallel configuration' of its [Ti₅NbO₅]^3- 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 2 lithium through a first-order transformation leading to a capacity of 100 mA h g^-1 at a potential of 1.67 V vs. Li/Li⁺.