Surface modifications of electrode materials for lithium-ion batteries: status and trends

The research on the electrodes of Li-ion batteries aims to increase the energy density and the power density, improve the calendar and the cycling life, without sacrificing the safety issues. A constant progress through the years has been obtained owing to the surface treatment of the particles, in particular the coating of the particles with a layer that protects the core region from side reactions with the electrolyte, prevents the loss of oxygen, and the dissolution of the metal ions in the electrolyte, or simply improve the conductivity of the powder. The purpose of the present work is to review the different surface modifications that have been tried in the past for the different electrodes that are currently commercialized, or considered as promising, including the three families of positive electrodes (lamellar, spinel, and olivine families) and the three negative electrodes (carbon, Li₄Ti₅O₁₂, and silicon). The role of the different coats used to improve either the surface conductivity, or the thermal stability, or the structural integrity is discussed. The limits in the efficiency of these different coats are also analyzed along with the understanding of the surface modifications that have been proposed.     

Maximizers for the Stein–Tomas Inequality

We give a necessary and sufficient condition for the precompactness of all optimizing sequences for the Stein–Tomas inequality. In particular, if a well-known conjecture about the optimal constant in the Strichartz inequality is true, we obtain the existence of an optimizer in the Stein–Tomas inequality. Our result is valid in any dimension.     

Towards a Certified Version of the Encyclopedia of Triangle Centers

Triangle centers such as the center of gravity, the circumcenter, the orthocenter are well studied by geometers. Recently, under the guidance of Clark Kimberling, an electronic encyclopedia of triangle centers (ETC) has been developed, it contains more than 7000 centers and many properties of these points. In this paper, we describe how we created a certified version of ETC such that some of the properties described come along with a computer checked proof of its validity.     

Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl

Grignard reagents RMgCl and their so‐called turbo variant, the highly reactive RMgCl?LiCl, are of exceptional synthetic utility. Nevertheless, it is still not fully understood which species these compounds form in solution and, in particular, in which way LiCl exerts its reactivity‐enhancing effect. A combination of electrospray‐ionization mass spectrometry, electrical conductivity measurements, NMR spectroscopy (including diffusion‐ordered spectroscopy), and quantum chemical calculations is used to analyze solutions of RMgCl (R=Me, Et, Bu, Hex, Oct, Dec, iPr, tBu, Ph) in tetrahydrofuran and other ethereal solvents in the absence and presence of stoichiometric amounts of LiCl. In tetrahydrofuran, RMgCl forms mononuclear species, which are converted into trinuclear anions as a result of the concentration increase experienced during the electrospray process. These trinuclear anions are theoretically predicted to adopt open cubic geometries, which remarkably resemble structural motifs previously found in the solid state. The molecular constituents of RMgCl and RMgCl?LiCl are interrelated via Schlenk equilibria and fast intermolecular exchange processes. A small portion of the Grignard reagent also forms anionic ate complexes in solution. The abundance of these more electron‐rich and hence supposedly more nucleophilic ate complexes strongly increases upon the addition of LiCl, thus rationalizing its beneficial effect on the reactivity of Grignard reagents.     

Detrimental Ni(0) transfer in Kumada catalyst transfer polycondensation of benzo[2,1‐b:3,4‐b']dithiophene

This article deals with the Kumada Catalyst Transfer Polycondensation (KCTP) of 4,7‐dioctylbenzo[2,1‐b:3,4‐b']dithiophene ( BDP‐Oct ) using Ni(II) catalyst or In/cat combination. A combination of MALDI MS, GPC, and ³¹P NMR spectroscopy is used to reveal the failure of the KCTP of this particular monomer. Intermolecular transfer reactions to monomer appeared to prevent the formation of polymer. This result is remarkable, since isomeric benzo[1,2‐b:4,5‐b']dithiophene polymerizes in a controlled way. The presence of a “non‐aromatic double bond” in annulated monomers is discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1706–1712     

On the Structure of the Ergosurface of Pomeransky-Senkov Black Rings

We study the properties of the ergosurface of the Pomeransky–Senkov black rings, and show that it splits into an “inner” and an “outer” region. As for the singular set, the topology of the “outer ergosurface” depends upon the value of parameters.