A furnace is described for in situ X-ray diffraction studies, in transmission mode, of structural changes in electrode materials for Li-ion (polymer) batteries in the ambient to 300°C temperature range. The method exploits the thin flat-cell geometry of the lithium-polymer battery concept. The flat sample is able to oscillate about a horizontal axis in its own plane in the X-ray beam, to provide better averaging during the diffraction experiment. The use of the device is demonstrated in a study of lithium intercalation in graphite (a commonly used anode material in lithium-ion batteries) during electrochemical cycling and storage at 70°C.

It is demonstrated here that the electron redistribution occurring as lithium becomes incorporated into or extracted from a crystalline transition-metal oxide (TMO) host can be studied experimentally by single-crystal X-ray diffraction (XRD) for the case of V6O13. The crystals pass through a sequence of LixV6O13 phases (x = 0, 0.5, 1, 2, 3 and 6) as lithium ions are incorporated into the V6O13 structure on discharging a [Li\liquid electrolyte\V6O13] cell from 3.2 to 1.8 V. The so-called deformation electron-density refinement of the electron distribution is exploited to extract the number of electrons associated with the Li, V and O atoms in the structure, and hence the electron rearrangement taking place on lithium insertion. This type of study is ultimately capable of identifying the complete sequence of oxidation-state changes occurring during the entire lithium insertion process in V6O13. (C) 1999 Elsevier Science S.A. All rights reserved.

An electrochemical cell has been constructed for in situ neutron diffraction studies of lithium-insertion/extraction processes in electrode materials for Li-ion batteries. Its key components are a Pyrex tube, gold plated on its inside, which functions as a current collector, and a central lithium rod, which serves as the negative electrode. The device is demonstrated here for a neutron diffraction study of lithium extraction from LiMn 2 O 4 : a mechanical Celgard © separator soaked in the electrolyte surrounds the lithium electrode. The LiMn 2 O 4 powder, mixed with electrolyte, occupies the space between separator and current collector.

An attachment is described for in situ X-ray diffraction studies in transmission mode of ion insertion processes in potential electrode materials. The method exploits the flat-cell geometry of the lithium polymer battery concept, in which the cell components are selected in order to expose the electrochemical process of interest. The flat sample is able to oscillate in the X-ray beam to provide a more representative diffractogram. An example of the use of the device is given.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

V6O13 microcrystalline powder was studied in an effort to resolve the stoichiometric effects. The Raman scattering spectrum of stoichiometric V6O13 microcrystalline powder is reported. The results are compared to the Raman scattering spectrum of V2O5 and VO2 polycrystalline materials obtained by annealing V6O13. Nous étudions les propriétés vibratoires du composé stoechiométrique V6O13 sous forme de poudre microcristalline. Le spectre de diffusion Raman est présenté. Une comparaison est menée avec les spectres des composés V2O5 and VO2 polycristallins obtenus par traitement thermique de V6O13.

There is a considerable lack of detailed information on the structure of lithiated phases of popular-consensus positive electrode materials for lithium/polymer and lithium-ion/polymer batteries. Having illustrated this phenomenon for the specific cases of LiMn2O4 and V6O13, some suggestions are made to present the problem in a more general context. The need for single-crystal diffraction studies is indicated.

We have studied the structme and conductivity of perovskite-type Lao.sSro.2Gao.ssMgo.Js02.825. the new, supe1ior oxygen ion conductor (1, 2) for use as electrolyte in high temperatme solid oxide fuel cells.Since the transpmt prope1ties of substitutionally disordered and oxygen deficient matelials are largely determined by their local structure, which may differ in symmetry from the average long range Clystalline symmetry, we studied the local and average structures of Lao.sSli).2Gao.ssMgo.Js02.825using powderneutr•on and electr•on diffraction and high resolution lattice imaging in TEM.Despite the macroscopic cubic symmetr)' revealed by neuu•on powder diffraction, Lao.sSro.2Gao.ssMgo.Js02.825exhibits a lower symmetry shmt range order evidenced by, firstly, weak and sharp superstr11ctme reflections and, secondly, str•eaks of diffuse scatte1ing in the electr•on diffraction patterns.Neutron powder profile refinement shows that tl1e oxygen nuclei are displaced from tl1e sites of cubic symmetry in a manner similar to tl1at in perovskite-related layered structme of brmvnmille1ite.Them1al stability of the local structmes was studied by high temperature electron diffraction and will be discussed in relation witl1 the conductivity measurements.Modeling of the oxygen mobility was perfmmed using the bond valence method (3).