Li-V-O Compounds

LiVOj is isostructural with LiCoO it has a da ratio of 5.20 (space group R3m ) [74]. Unlike LiCoO, and LiNiOj, LiVOj is unstable to delithiation at x 0.3 inLi,, .V02, the vanadium ions become mobile and diffuse from the octahedral sites (3b) of the vanadium layer into octahedral sites (3a) left vacant by the extracted lithium ions. The diffusion of vanadium ions takes place through face-shared tetrahedra linking the octahedra of alternate layers and is believed to occur by a disproportionation reaction in which ions occupy tetrahedral (6c) sites [74, 751  

The disproportionation reaction destroys the layered structure and the two-dimensional pathways for lithium-ion transport. For jr 0.3, delithiated Lij VO, has a defect rock salt structure without any well-defined pathways for lithium-ion diffusion. It is, therefore, not surprising that the kinetics of lithium-ion transport and overall electrochemical performance of Li, .V02 electrodes are significantly reduced by the transformation from a layered to a defect rock salt structure [76]. This transformation is clearly evident from the 

Vanadium oxides are attractive candidates as insertion electrodes for lithium batteries because three stable oxidation states (, 

V and V ) can be accommodated within a close-packed oxygen array. 

The layered structure of Li,2V30g was first determined by Wadsley in 1956 [83] (Fig. 9a) it has monoclinic symmetry (space group P2, /m). 

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