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The -Li x V 2 O 5 phase (0.4 р x р 3) has been investigated as rechargeable cathodic material for lithium batteries. The interest in using the phase as rechargeable electrode consists in the stability of its tetragonal structure (⌬V/V Ͻ 1%) as the Li insertionextraction proceeds. Lithium ions are found to be responsible for the ordering of the structure. AC impedance measurements have shown important kinetic limitations appear in the Li composition range 2.2 р x р 3, hindering the use of high current densities. However, at C/20 rate a remarkable and stable specific capacity of 310 mAh g Ϫ1 is obtained over 30 cycles. Its cycling behavior in the 3.8/1.5 V voltage window has been shown to strongly depend on the C rate and temperature. At a higher rate ͑C/5͒, the capacity decline observed as galvanostatic cycling proceeds has been found to originate from a significant dissolution process of the vanadium oxide, leading to the presence of V IV and V III species in electrolyte.

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Micro-Raman spectrometry and x-ray diffraction (XRD) experiments were performed on the anatase Li x TiO 2 system .0 ≤ x ≤ 0.6/ produced from the electrochemical discharge of a TiO 2 composite cathode in propylene carbonate -LiClO 4 solution at room temperature. Raman spectrum modifications indicate local structural and chemical changes as lithium enters the anatase host lattice. The existence of a tetragonal to orthorhombic phase transition is clearly demonstrated by the Raman and XRD measurements. Moreover, lithium extraction is only partially quantitative for Li uptake ≤0.5, as shown both from structural and electrochemical data in the 3-1.5 V potential range. For the first time, the Raman fingerprint of the lithium titanate (LT) Li 0.5 TiO 2 orthorhombic phase is clearly evidenced. A theoretical analysis of the lattice dynamics suggested a complete interpretation of the experimental Raman spectra in the Li x TiO 2 system, which provided valuable information on the Li atom positions and coordination in LT. Taking into account the possibility of rather short Li-O distances, the complex band structure in the high-wavenumber region is assigned to the Li-O vibrations. Furthermore, spectra simulation offers an explanation for the new shape of the TiO 2 lattice modes observed in the low-wavenumber region.

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Studying the electronic transport in Li x MoO3 powders is of the utmost interest due to the strong influence of the grain size and morphology on their electrochemical cycling properties. An original straightforward synthesis method permitted the obtaining of nanobelts of α-MoO3 with a slightly better reversibility of Li insertion−deinsertion and a higher efficiency of the lithium insertion process. The broad-band dielectric spectroscopy technique from 40 to 1010 Hz was applied to Li x MoO3 micronic powder and nanobelts. Dielectric relaxations were found, attributed to polarons and bipolarons motions. The role of the morphology and size effect has been investigated by comparing the electron transport properties of micronic powder and nanobelts. Particle size effect is evidenced giving rise to different thermal behaviors between the two types of powders. This work opens up new prospects for a more fundamental understanding of the electronic transport in relation to the electrochemical properties of α-MoO3.