5006-97-3Relevant academic research and scientific papers
Solid-state chemistry of ammonium and cesium 1-vanado-11-molybdophosphate and ammonium 12-molybdosilicate: Application to oxidation catalysis
Laronze,Marchal-Roch,Guillou,Liu,Herve
, p. 172 - 181 (2003)
The solid-state behavior of (NH4)4[PMo 11VVO40], crystallized from a water/dioxane solution, has been studied. Decomposition of one of the four ammonium cations occurs easily and a thermal treatment in air at 220°C leads to (NH 4)3H[PMo11VO40]. Further ammonium decomposition was observed between 220 and 300°C up to (NH4) 0.8H3.2[PMo11VO40]. Only one cubic phase was evident and the lattice parameter increases as ammonia is eliminated. Rietveld refinement of X-ray patterns of all samples is better with an occupancy of 34 for anionic sites, as previously proposed for Cs 4[PMo11VO40]. Solid-state substitution of cesium for ammonium cations has been performed by thermal treatments at 300°C of the ammonium salt impregnated by cesium nitrate. Only three ammonium cations can be substituted. The catalytic behavior of these salts for the oxidative dehydrogenation of isobutyric acid reveals high catalytic activity and selectivity to methacrylic acid for all the samples up to three cesium cations but fall down hereafter.
Understanding formation of solid electrolyte interface film on LiMn2O4 electrode
Zhang,Xu,Jow
, p. A1521-A1526 (2002)
We studied formation of solid electrolyte interface (SEI) film on the surface of spinel LiMn2O4 electrodes by evaluating irreversible capacity and monitoring impedance change in the first charge and discharge cycle of a Li/LiMn2O4 cell. Results show that during the first cycle, LiMn2O4 produces 10-15% irreversible capacity in both 1 m LiPF6 3:7 ethylene carbonate/ethyl methyl carbonate (EC/EMC) and 1 m LiPF6 1:1:3 propylene carbonate (PC)/EC/EMC electrolytes. Formation of the irreversible capacity mainly takes place in two voltage regions of ～3.1 V, near open-circuit voltage of a fresh cell, and 3.7-4.2 V, in the voltage range of delithiation and lithiation of LiMn2O4. It is believed that the irreversible capacity is associated with the formation of SEI film on the surface of LiMn2O4 electrode. Impedance data indicate that electrolyte solvents greatly affect properties of the SEI film. The SEI film formed with PC/EC/EMC electrolyte is more resistive and more stable, while that formed with EC/EMC electrolyte is subjected to a reversible breakdown at voltages higher than 3.8 V. It is observed that after the cell is cycled, the SEI film becomes more conductive while the bulk resistance of electrolyte and electrode increases.
