Lithium Insertion in an Oriented Nanoporous Oxide with a Tunnel Structure: Ti₂Nb₂O₉

The electrochemical study of the empty tunnel structure Ti 2 Nb 2 O 9 shows that it can intercalate lithium reversibly, through a solid−solution process, leading to the phase Li 4 Ti 2 Nb 2 O 9 . The high-resolution electron microscopy study of this phase shows that Ti 2 Nb 2 O 9 exhibits an exceptional nanoporosity, involving the formation of aligned holes throughout the whole microcrystal, which may favor, together with the presence of tunnels, the diffusion of lithium during the insertion. The reversible capacity of this phase, of 125 mAh/g at 1.57 V vs Li/Li +, after 30 cycles, shows its great reversibility.