Sn-Sb and Sn-Bi alloys as anode materials for lithium-ion batteries

Sn/SnSb, Sn/Bi, and Sn/SnSb/Bi multi-phase materials were synthesised via reduction of cationic precursors with NaBH₄ and with Zn, and were tested for their suitability as anode materials for Li-ion batteries by galvanostatic cycling. The rapid reduction with NaBH₄ yielded the finer materials with the better cycling stabilities, whereas the reduction with Zn yielded the purer materials with the lower irreversible capacities in the first cycle. Reversible capacities of ∼ 600 mAh g⁻¹, ∼ 350 – 400 mAh g⁻¹, and ∼ 500 mAh g⁻¹ were obtained for Sn/SnSb, Sn/Bi, and Sn/SnSb/Bi, respectively. The cycling stability of the materials decreased in the order Sn/SnSb>Sn/SnSb/Bi>Sn/Bi, which is in part attributed to the presence / absence of intermetallic phases which undergo phase-separation during lithiation. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Coordination of aza heterocycles with macroheterocyclic metal complexes in amphiprotic media: III. Kinetics and mechanism of inner-sphere ligand exchange in (tetraphenylporphyrinato)chromium(III)

Inner-sphere replacement of alcohols by imidazole and its derivatives in the complex (acetato)-(tetraphenylporphyrinato)chromium(III) was studied by electronic absorption spectroscopy. The rate constants and activation parameters of the process were calculated. The entering ligand structure was shown to affect the reaction rate, while the alcohol nature (departing ligand) does not influence the kinetic parameters of the process to an appreciable extent. Regression analysis revealed participation of imidazole and ethanol in the rate-determining stages. The kinetic equation for the inner-sphere axial substitution implies interaction of a free alcohol molecule with that coordinated to chromium, followed by replacement of the associate by the heteroring. Mathematical processing of the kinetic data in terms of the proposed solvolytic association-dissociation mechanism gave the rate constants for particular stages of the process and showed an extremal relation between the rate constant and composition of the solvent.     

The Active Mixed Anhydrides of Phosphorous Ph-Acids

Abstract

The ³¹P spectra of H₃PO₃ + Ac₂O and PCl₃ + Ac₂O contain signals which were assigned to the following compounds (δ_p, J_pH): H₃PO₃(8,5; 702), AcO(OH)P(O)H (2,2; 739), (AcO)₂P(O)H (-2,7; 763), (AcO)₃P (131,6); PCl₃ (220,7), AcOPCl₂ (194,6), (AcO)₂PCl (167,O), (AcOl₃P (131,5). The active intermediates with -PH(O)Cl groups are formed on treating phosphorous PH-acids with AcCl, and in other reactions¹. These intermediates are added to aldehydes and ketones resulting in compounds (I), (11) and (111). The compounds of type (11) treated with AcOH transform into compounds of different structure, e.g. into (IV) and (V).     

Desulfurization of tall oil pitch

Method for desulfurization of tall oil pitch is suggested. The method is based on successive treatments with hydrogen peroxide, sulfuric acid, and aqueous solutions of acetonitrile. As a result, the total content of sulfur was reduced from 3800 to 220 ppm. The fuel characteristics of the desulfurized pitch were determined. The purified pitch can be used in the conventional areas of its application, in which restrictions are imposed on the total content of sulfur.     

New large-scale production route for synthesis of lithium nickel manganese cobalt oxide

The spray roasting process is recently applied for production of catalysts and single metal oxides. In our study, it was adapted for large-scale manufacturing of a more complex mixed oxide system, in particular symmetric lithium nickel manganese cobalt oxide (LiNi_1/3Co_1/3Mn_1/3O₂—NMC), which is already used as cathode material in lithium-ion batteries. An additional lithiation step was coupled with the main process in order to obtain the desired layered structure. Thermogravimetric analysis and high-temperature X-ray diffractometry built the basis for determining suitable synthesis temperature regions for the used chloride precursors and the post-treatment step. The optimized process was proven on an industrial pilot line where a setup for minimum production capacity of 12 kg h^?1 was possible. The powder obtained directly after roasting had a very striking morphology compared to the final lithiated product. Hollow aggregates (≥250 μm) with overall 10.926 m² g^?1 surface area and a pore diameter of 3.396 nm were observed. Their well-faceted primary particles were converted into nanosized spheres after lithiation, building a few micrometer big high-porous agglomerates. Actual composition was verified by inductively coupled plasma atomic emission spectroscopy analysis, and the crystal structure and corresponding unit cell parameters were identified and confirmed by Rietveld fit of the derived X-ray diffraction pattern. The initial electrochemical measurements show a 149-mAh g^?1discharge capacity, as determined from cyclic voltammetry.