3 . -Lithium intercalation compounds based on lithium manganese oxides are of great importance as positive electrodes for rechargeable lithium batteries. Mn 4+ compounds such as the title compound are considered electrochemically inert due to their inability to oxidize Mn 4+ . As revealed by powder XRD, SEM, XPS, and electrochemical measurements substantial quantities of Li (at least 1.39 Li) may be removed from the title compound, without Mn oxidation, by either proton exchange (at 55°C) or simultaneous Li and oxygen removal followed by proton exchange (at 30°C)

The electrochemical activity of Li2MnO3 in non-aqueous media has been investigated and found to involve neither Mn(4+)-Mn5+ oxidation nor simultaneous O2- removal but exchange of Li+ by H+, the latter being generated in the electrolyte.

No abstract

The stoichiometry, stability and polymorphism of the perovskite-related solid solutions, Lio,-~REo,,+,TiO, : RE = La, Nd, has been studied. For both series, the data are presented in the form of a temperature vs. composition phase diagram. Unit cell data for the different polymorphs (three in the La system, four in the Nd system) are presented, together with data on the composition and thermal history dependence of the lattice parameters. The phase composition and microstructure of selected ceramic samples were analysed by electron microprobe techniques.

with the O3 (RNaFeO 2 ) structure has been prepared from the analogous P3 sodium phase by ion exchange using LiBr in either ethanol at 80 °C or hexanol at 160 °C. The former preserves, to some extent, vacancies present on the transitional metal sites of the sodium phase, whereas the latter eliminates the vacancies. Materials with vacancies exhibit better performance as cathodes in rechargeable lithium batteries. The 2.5% Co doped material prepared in ethanol exhibits capacities of 200 mAhg -1 when cycled at C/8 between 2.4 and 4.6 V at 30 °C and with a fade of only 0.08% per cycle. A capacity of 180 mA h g -1 can be obtained at C/2 and 200 mAhg -1 at C rate and 55 °C. Importantly, this performance is obtained despite the fact that the materials convert to spinel-like phases on cycling. The spinel-like phases that form are nanostructured, with each crystallite being composed of a mosaic of nanodomains. The relief of strain at the domain wall boundaries accompanying the cubic-tetragonal phase transition may explain, at least in part, the facile cycling of these materials over a wide composition range (including the 3 V plateau) compared with high-temperature spinel which does not possess such nanodomains. Furthermore, vacancies present in the ethanol materials appear to migrate to the domain walls on cycling, rendering even more facile the Jahn-Teller-driven phase transformation on cycling these materials compared with those prepared in hexanol.