• Energy Research

Abstract not Available.

The incorporation of fly ash from olive biomass (FAOB) combustion in cogeneration plants into cement based mortars was explored by analyzing the chemical composition, mineralogical phases, particle size, morphology, and IR spectra of the resulting material. Pozzolanic activity was detected and found to be related with the presence of calcium aluminum silicates phases. The preparation of new olive biomass fly ash content mortars is effective by replacing either CaCO(3) filler or cement with FAOB. In fact, up to 10% of cement can be replaced without detracting from the mechanical properties of a mortar. This can provide an alternative way to manage the olive biomass fly ash as waste produced in thermal plants and reduce cement consumption in the building industry, and hence an economically and environmentally attractive choice.

Abstract The electrochemical performance of a Li-ion battery made from nanometric, highly crystalline LiNi 0.5 Mn 1.5 O 4 as positive electrode and mesoporous carbon microbeads (MCMBs) as negative electrode was assessed. The best performance was obtained by using a slight excess of spinel (a cathode/anode mole ratio of 1.3) and lithium bis-oxalate borate (LiBOB) instead of LiPF 6 as an electrolyte salt. Higher spinel contents caused the formation of metallic Li in the carbon and the rapid degradation of battery performance as a result. The calculated output energy was 322 Wh kg −1 which is higher than the value reported for the LiMn 2 O 4 /C cell (250 Wh kg −1 ).

Carbon fibers obtained by pyrolysis of tailored resorcinol/formaldehyde polymer particles were used to anchor Si nanoparticles at their surface. The carbonization process, carried out at 1000 °C under nitrogen, induced strong interactions between Si particles and the carbon matrix through a thick amorphous silicon oxide layer as revealed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Therefore, the actual composition of the composites was Si/SiOx/C (fibers). Component contents were determined from thermogravimetric measurements (TG) made under oxygen. The composites delivered specific capacities as high as 2500 mA h gSi−1 at rather high current densities (500 mA gsi−1) and exhibited good capacity retention on cycling. By contrast, a mixture of pristine Si nanoparticles and carbon nanofibers performed considerably worse, their capacity fading abruptly with cycling. The improved performance of composites is ascribed to a combination of the properties of the amorphous SiOx layer, and the texture and morphological properties of carbon, increasing the electrode conductivity and buffering Si expansion and shrinkage during Li insertion and deinsertion.

A synergistic combination between a biomass carbon derived from avocado seeds and a conductive copolymer has been employed to obtain high-energy and sustainable lithium–sulfur batteries.

The other polymorph: A vapor-phase route for the fabrication of β-Fe(2)O(3) nanomaterials on Ti substrates at 400-500 °C is reported. For the first time, the β polymorph is tested as anode for lithium batteries, exhibiting promising performances in terms of Li storage and rate capability.

In the last few years, several strategies towards boosting the electrochemical performance of LiFePO4 cathodes have been envisaged. Copper addition to the phosphate seems to be a simple, inexpensive method for this purpose. However, it has a serious drawback: at voltages slightly higher than that required for lithium extraction from LiFePO4, the copper is oxidized to either Cu(I) or Cu(II) with partial decomposition of the electrolyte. XRD patterns are consistent with the disappearance of copper from pristine composites upon charging at up to 4.0 V. Moreover, a copper deposit is formed on the lithium surface in the discharged state that creates a barrier hindering the release of Li ion from the electrode. Therefore, copper electroactivity strongly influences the capacity and cycling life of the cell. © 2007 Elsevier Ltd. All rights reserved.

Abstract Fine powders of tin dioxide doped with Mo were prepared under hydrothermal conditions and tested in lithium cells. X-ray and IR data revealed the formation of single-phase products with a rutile-like structure that is maintained upon calcining at 800°C. Mo 6+ ions change the habit growth of crystals and are randomly distributed at octahedral positions, thus promoting the formation of cation vacancies. The addition of Mo increases the reversibility of the lithium insertion/de-insertion process, as reflected in the simplified differential specific capacity plots obtained, which result in a single, rather symmetric peak in the anodic and cathodic waves. Furthermore, increasing the Mo content improves retention capacity at the expense of reversible capacity because the transition element acts as an inactive component in the electrochemical process. The following arguments account for the improved performance of these mixed oxides. (i) A diluent effect of Mo atoms that facilitates dispersion of the Sn atoms formed during the reduction process; (ii) hindered formation of large clusters and decreased interfacial strains; (iii) restriction of the number of alloying/de-alloying processes through a decreased reversible capacity during the first few cycles; and (iv) an increased chemical diffusion coefficient for lithium, that results partially from the structural disorder caused by the replacement of tin with molybdenum.

spinels (M 5 Cr, Ni, Cu;x ’ 0.2) prepared at 500°C was analyzed by using accurate analytical spectroscopic techniques ~mass spectroscopy, nuclearmagnetic resonance! to examine the electrolyte behavior. The spectra revealed organic solvents to be stable as no decompositionproducts were detected, thus excluding the electrolyte oxidation as a side reaction accounting for the cell overcharge. However,these spinels contain excess oxygen in an amount that was quantified from thermogravimetric data. The excess oxygen plays aprominent role in the electrochemical response of the spinel. The cyclic voltammetry and galvanostatic results support theassumption that the excess oxygen can be released above 4.5 V. The additional capacity obtained and that required to release theoxygen were quite consistent. This must be the origin of both the overcharge and the poor performance of the cells compared withspinels of similar composition but synthesized at higher temperatures ~800°C!, the excess of oxygen in which was smaller.© 2004 The Electrochemical Society. @DOI: 10.1149/1.1824037# All rights reserved.Manuscript submitted March 30, 2004; revised manuscript received May 20, 2004. Available electronically November 17, 2004.