51V magic angle spinning solid state NMR studies of Bi4V2O11 in oxidized and reduced states

Prospects of oxide ionic conductivity bismuth vanadate-based solid electrolytes

“…The data are consistent with distorted oxygen octahedral around Cu with a compression of the apical oxygen. In addition, they reported that V is present predominantly as V 5+ rather than V 4+ , which is in contrast with the results reported by Delmaire et al (2000) on the reduction of Bi 4 V 2 O 11-δ under a hydrogen flow. Here, the reduction of V 5+ to V 4+ leads to the formation of Bi 4 V 2 O 10.66 .…”

Practical aspects of 51V and 93Nb solid-state NMR spectroscopy and applications to oxide materials

“…According to 51 V NMR data reported by Delmaire et al [189] there are at least three different vanadium sites in a-Bi 4 V 2 O 11 , two of these sites are tetrahedral and one is in bipyramidal trigonal or has a distorted octahedral oxygen coordination. The majority of the vanadium (about 70%) occupies regular tetrahedral sites and the rest is found in bipyramidal trigonal or distorted octahedral sites.…”

Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide

“…37-39 51 V shifts of ~-550 ppm are not therefore characteristic of V(V) sulphides and are more commonly exhibited by the vanadium oxides (vanadates). 40,41 However, it has been observed that reduction of V(V) to form mixed valent V(IV)/ V(V) vanadium oxides can result in large negative shifts from ~-550 ppm to ~-1440 ppm. 41 Thus, the negative shift from 1440 ppm to -547 ppm is similarly ascribed to partial reduction of V(V) to V(IV) as the discharge progresses.…”

“…40,41 However, it has been observed that reduction of V(V) to form mixed valent V(IV)/ V(V) vanadium oxides can result in large negative shifts from ~-550 ppm to ~-1440 ppm. 41 Thus, the negative shift from 1440 ppm to -547 ppm is similarly ascribed to partial reduction of V(V) to V(IV) as the discharge progresses. The huge shift in the Li NMR spectrum for Li = 2.0 exhibits a broad feature at ~25 ppm further supporting the formation of a paramagnetic material comprised of both V(IV) and V(V).…”