Topotactic Transformation of the Cationic Conductor Li4Mo5O17 into a Rock Salt Type Oxide Li12Mo5O17

Intercalation of lithium in the ribbon structure Li4Mo5O17 has been achieved, using both electrochemistry and soft chemistry. The ab initio structure determination of the "Mo-O" framework of Li12Mo5O17 Shows that the [Mo5O17](infinity) ribbons keep the same arrangement of edge sharing MoO6 octahedra and the same orientation as in the parent structure but that a topotactic antidistortion of the ribbons appears, as a result of the larger size of Mo4+ in "Li-12" compared to Mo6+ in "Li-4". On the basis of bond valence calculations, it is observed that 12 octahedral sites are available for Li+ in the new structure so that an ordered hypothetical rock salt type structure can be proposed for Li12Mo5O17. After the first Li insertion, a stable reversible capacity of 100 mA . h/g is maintained after 20 cycles. A complete structural reversibility leading back to the ribbon type Li4Mo5O17 structure is obtained using a very low rate of C/100. The exploration of the Li mobility in those oxides shows that Li4Mo5O17 is a cationic conductor with sigma = 10(-3.5) S/cm at 500 degrees C and E-a = 0.35 eV.