Direct Observation of XRD Redox Processes In Tmo's

摘要

Accurate XRD, often in combination with ND, has long been used ot study electron denisty features in crystalien compouns .THe method is particularly succcessful for lightatom systems in which the valence-to-core electron ratio is high. The same method is clearly applciable to the study of lithium insertion/extraction porcesses in TMO compounds; the greatest hinder has been the availability of sufficiently large single crystals, which do not then disintegrae into micron-size particles during the reaction. The case of V_6O_13 is especially advantatgeous in this context, howwever: millimeter-size crystals can be grown y CVT methods, which do not then exhibit severe cracking on lithium insertion, probably as a result of the layer-like natue of the structure. A sequence of single-crystal phases have now been studied in this way folowing in situ electrochemical synthesis in the copostie cathode of a

half-cell. The resulting structures have been solved, and their associated electron-density distributions carefully analysed byso-caled Hirshfeld deformation electron density refinement. The method would appear to provide meningful information relating to oxidation state changes occurring on lithium-ion insertion.