Direct evidence of oxygen evolution from Li1+ x (Ni1/3Mn1/3Co1/3)1− x O2 at high potentials

Li1+x (Ni1/3Mn1/3Co1/3)1−x O2 (NMC) oxides are among the most promising positive electrode materials for future lithium-ion batteries. A voltage "plateau” was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5V vs. Li/Li+ for compounds with x>0 (overlithiated compounds). Differences were observed in the cycling stability of the overlithiated and stoichiometric (x=0) NMC oxides in this potential region. A differential plot of the charge vs. potential profile in the first cycle revealed that, for the overlithiated compounds, a large irreversible oxidative peak arises positive to 4.5V vs. Li/Li+, while in the same potential region only a small peak due to the electrolyte oxidation is detected for the stoichiometric material. Differential Electrochemical Mass Spectrometry (DEMS) was used to investigate the high voltage region for both compounds and experimental evidence for oxygen evolution was provided for the overlithiated compounds at potentials positive to 4.5V vs. Li/Li+. No oxygen evolution was detected for the stoichiometric compoun

DTM segmentation and analysis for archaeological hill-top sites recognition in GRASS

This paper presents a procedure for the automatic creation of a map of probable location of archeological hill-top sites, i. e. sites on dominant positions with respect to surrounding areas, from a digital terrain model. These areas are detected by combining segmentation techniques and morphological filtering. The application of a segmentation technique to the DTM creates two maps showing respectively homogenous areas and discontinuities, according to some criteria. The following application of filtering to the homogenous areas selects areas with a suitable combination of minimum surface, maximum value of compactness and maximum mean curvature. The result of the procedure is a map of candidate hill-top sites, which is used by archeologists for further analysis. Besides the specific application, this study provides an example of the usage of the GRASS r.seg modules with indication about the choice of suitable values for the required parameters. The study has been carried out on the whole Provincia Autonoma di Trento (north east Italy)

First-principles material modeling of solid-state electrolytes with the spinel structure

Ionic diffusion through the novel (AlxMg1-2xLix)Al2O4 spinel electrolyte is investigated using first-principles calculations, combined with the Kinetic Monte Carlo algorithm. We observe that the ionic diffusion increases with the lithium content x. Furthermore, the structural parameters, formation enthalpies and electronic structures of (AlxMg1-2xLix)Al2O4 are calculated for various stoichiometries. The overall results indicate the (AlxMg1-2xLix)Al2O4 stoichiometries x = 0.2…0.3 as most promising. The (AlxMg1-2xLix)Al2O4 electrolyte is a potential candidate for the all-spinel solid-state battery stack, with the material epitaxially grown between well-known spinel electrodes, such as LiyMn2O4 and Li4+3yTi5O12 (y = 0…1). Due to their identical crystal structure, a good electrolyte-electrode interface is expected.status: publishe