摘要:

Vanadium pentoxide deposits have been prepared by electrochemical oxidation of vanadyl ions in aqueous solution. They were characterized with the use of a combination of techniques including: X-ray diffraction, TGA, SEM, chemical titration… They exhibit a 2D structure similar to that of V2O5gels and contain the same number of exchangeable protons and water molecules per formula unit. However clear differences are also observed, mainly related to the V4+content, the interlayer distance and their evolution with thermal treatments.

ISSN:1058-725X    

DOI:10.1080/10587259808042369

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Lithiated spinel manganese oxides with various amounts of lithium have been prepared through solid-state reaction and electrochemical intercalation and deintercalation. Structures of the LixMn2O4samples with 0.3≤x≤1.2 are studied using X-ray diffraction and Rietveld refinement techniques. We report vibrational spectra of lithiated manganese oxides as a function of lithium concentration. The spectra of lithiated spinel manganese oxides have been analyzed on the basis of LiO4tetrahedra and MnO6octahedra when Li/Mn≤0.5, and LiO4, LiO6, and MnO6structural units when Li/Mn>0.5. Electrochemical performances of lithium manganese oxide are also studied.

ISSN:1058-725X    

DOI:10.1080/10587259808042370

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The phonons in superconducting oxide spinel LiTi2O4are investigated using a short range force constant model (Model I) and a modified rigid ion model (Model II), including the long range Coulomb electrostatic interaction. The phonons, in which lithium atoms are involved, have been identified and their relation to the long range Coulomb interaction discussed.

ISSN:1058-725X    

DOI:10.1080/10587259808042371

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Addition of a surface active agent during hydrolysis of vanadium alkoxide allows to slow the gelification rate and to control the viscosity of the gel. Furthermore, after the surfactant elimination, the porosity of V2O5greatly increases. Consequently, the electrochemical specific capacity and the specific energy increase. Lithium is intercaled into V2O5films up to a stoichiometry of 2.5 moles Li per mole V2O5(3.5 < V vs Li < 1.9). Diffusivity coefficient of layers containing surfactant is hundred times higher than in classical V2O5xerogel.

ISSN:1058-725X    

DOI:10.1080/10587259808042372

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

HREM study of stacking faults in O-LiMnO2is presented as a confirmation of the previous model obtained from XRD measurements.

ISSN:1058-725X    

DOI:10.1080/10587259808042373

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of octahedral Mn vacancies on lithium and proton intercalation in the spinel structure of lithium manganate is investigated by means of atomistic simulation techniques. Prefered insertion sites and migration pathways for Li ions in the interstitial space of the lattice are calculated. The computations indicate an energetic preference for both Li ions and protons to cluster around the octahedral defects to compensate the local charge.

ISSN:1058-725X    

DOI:10.1080/10587259808042374

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We show that the γ(III)/β(II) phase transition is at the origin of the second plateau at 0.8V in the Ni-based batteries by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies and intermittent galvanostatic measurements (GITT). This study shows that the equilibrium voltage of this transition is 1.25V vs Cd-Cd(OH)2, thus implying an overvoltage of 400 mV. Direct evidence for a textural memory effect trough the γ(III)/β(II) phase transition is given by TEM studies. The reoxidation of the β(II) phase to γ(III) phase occurs without going trough the β(III) phase.

ISSN:1058-725X    

DOI:10.1080/10587259808042375

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Effect of cobalt additive on the NiOOH/Ni(OH)2phase boundary movement has been investigated by analysing build-up and decay current transients under the application of various voltage steps(70 to 400 mV). The occurrence of current plateau upon hydrogen extraction from the completely hydrogen-injected films indicated that the hydrogen transport through the film proceeds by the movement of NiOOH/Ni(OH)2phase boundary. The velocity and mobility of the phase boundary movement upon hydrogen extraction were determined to be orders of 10−6cm s−1and 10−5cm s−1V−1in magnitude, respectively. It is concluded that β-Ni(OH)2phase is stabilised by the Co(OH)2incorporation into the Ni(OH)2film and hence both the velocity and mobility of the NiOOH/Ni(OH)2phase boundary movement is raised by the Co(OH)2incorporation.

ISSN:1058-725X    

DOI:10.1080/10587259808042376

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Chemical disorder of battery active manganese dioxides (MD) evidenced as Mn3+, Mn vacancies and OH groups, is associated to well identified structural defects. Structural analysis of ordered-disordered MD with increasing defects content relates Mn3+to inter growth defects (Pr) and Mn vacancies to micro twinning (Tw). Potentiostatic reduction studies in 1N KOH provide I(V) and V(x) curves which show a correlation between the potential of the maximum intensity of the reduction current, the chemical and associated structural defects and the reduction kinetics of respectively EMD, CMD and ramsdellite. Reversibility is obtained for the two first forms in oxidation.

ISSN:1058-725X    

DOI:10.1080/10587259808042377

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A relatively large negative magnetoresistance has been evidenced in intercalation compounds MnxTiS2(0 <x≤ 0.25) from measurements up to 31 T at 1.8, 4.2, and 77 K. For low Mn concentrationx≤ 0.03, Mn3delectrons are regarded as ‘localized’ spins with thermal fluctuation, while for higher concentrationx> 0.03, a ‘Mn-derived band’ is formed near the Fermi energy. In the layered structure of MnxTiS2, the carrier transport takes place along the host TiS2layers and through the interlayer spaces via intercalated Mn atoms. The observed negative magnetoresistance can be reasonably explained by existing spin fluctuation theories.

ISSN:1058-725X    

DOI:10.1080/10587259808042378

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor