Jorge E. Thomas

Electrochemical comparison of LiFePO4 synthesized by a solid-state method using either microwave heating or a tube furnace

LiFePO4/C composites were successfully prepared by a solid-state reaction in order to compare conventional heat treatment and microwave-assisted synthesis at different times of sintering. Microwave-assisted synthesis is interesting due to the fact that energy and inert gas consumption can be greatly reduced with respect to the conventional treatment, resulting in a cheaper synthesis method. The relationship between particle morphology and crystal structure using the composite synthesis was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) with refinements of the crystal structures carried out by the Rietveld method. In addition, the electrochemical performances were evaluated using constant current charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). It was observed that the samples prepared by microwave heating had a better electrochemical behavior than those prepared in a conventional furnace. Also, in general, a higher sintering time improved the electrochemical behavior, but with increased particle sizes, and consequently, a decreased specific capacity.Graphical Abstract

On the effect of the carbonaceous substrate in the nucleation of Sn nanoparticles for Li-ion anodes: experiments and first principles calculations

AbstractThe nucleation of Sn nanoparticles by chemical reduction was studied using three different carbonaceous substrates, to obtain Sn/C composites. When used as active materials in anodes for lithium-ion batteries, these composites displayed higher capacities than commercially used graphite, and showed a good cyclability. The differences in morphology, capacity, cyclability, and diffusion between the resulting materials are highlighted. The resulting materials were characterized by charge-discharge cycling, voltammetry, EIS, SEM, and TEM microscopy. It was found that the substrate has a determinant effect on the deposition of Sn. This effect is interpreted in terms of the relative adsorption energies of a single Sn atom obtained from DFT calculations. Graphical abstractᅟ