Unraveling the performance of dispersion-corrected functionals for the accurate description of weakly bound natural polyphenols

Long-range non-covalent interactions play a key role in the chemistry of natural polyphenols. We have previously proposed a description of supramolecular polyphenol complexes by the B3P86 density functional coupled with some corrections for dispersion. We couple here the B3P86 functional with the D3 correction for dispersion, assessing systematically the accuracy of the new B3P86-D3 model using for that the well-known S66, HB23, NCCE31, and S12L datasets for non-covalent interactions. Furthermore, the association energies of these complexes were carefully compared to those obtained by other dispersion-corrected functionals, such as B(3)LYP-D3, BP86-D3 or B3P86-NL. Finally, this set of models were also applied to a database composed of seven non-covalent polyphenol complexes of the most interest.FDM acknowledges financial support from the Swedish Research Council (Grant No. 621-2014-4646) and SNIC (Swedish National Infrastructure for Computing) for providing computer resources. The work in Limoges (IB and PT) is supported by the “Conseil Régional du Limousin”. PT gratefully acknowledges the support by the Operational Program Research and Development Fund (project CZ.1.05/2.1.00/03.0058 of the Ministry of Education, Youth and Sports of the Czech Republic). IB gratefully acknowledges financial support from “Association Djerbienne en France”

Accurate Treatment of Large Supramolecular Complexes by Double-Hybrid Density Functionals Coupled with Nonlocal van der Waals Corrections

In this work, we present a thorough assessment of the performance of some representative double-hybrid density functionals (revPBE0-DH-NL and B2PLYP-NL) as well as their parent hybrid and GGA counterparts, in combination with the most modern version of the nonlocal (NL) van der Waals correction to describe very large weakly interacting molecular systems dominated by noncovalent interactions. Prior to the assessment, an accurate and homogeneous set of reference interaction energies was computed for the supramolecular complexes constituting the L7 and S12L data sets by using the novel, precise, and efficient DLPNO-CCSD(T) method at the complete basis set limit (CBS). The correction of the basis set superposition error and the inclusion of the deformation energies (for the S12L set) have been crucial for obtaining precise DLPNO-CCSD(T)/CBS interaction energies. Among the density functionals evaluated, the double-hybrid revPBE0-DH-NL and B2PLYP-NL with the three-body dispersion correction provide remarkably accurate association energies very close to the chemical accuracy. Overall, the NL van der Waals approach combined with proper density functionals can be seen as an accurate and affordable computational tool for the modeling of large weakly bonded supramolecular systems.Financial support by the “Ministerio de Economía y Competitividad” (MINECO) of Spain and European FEDER funds through projects CTQ2011-27253 and CTQ2012-31914 is acknowledged. The support of the Generalitat Valenciana (Prometeo/2012/053) is also acknowledged. J.A. thanks the EU for the FP7-PEOPLE-2012-IEF-329513 grant. J.C. acknowledges the “Ministerio de Educación, Cultura y Deporte” (MECD) of Spain for a predoctoral FPU grant

Metallpulverspritzgießen bietet viele vorteile

Das MIM-Verfahren (Metal Injection Moulding; übersetzt: Metallpulverspritzgießen) ist ein hoch modernes Verfahren zur Herstellung metallischer Bauteile. Die Vorteile liegen in der Möglichkeit, sowohl geometrisch sehr komplexe Bauteile abzuformen, wie sie aus dem verwandten Kunststoffspritzgießen bekannt sind, als auch in der Freiheit der Materialauswahl. Selbst schwer zerspanbare Hochleistungswerkstoffe lassen sich vergleichsweise kostengünstig in Form bringen. Damit hat es die MIM-Technologie geschafft, sich in Industriezweigen wie Automobilbau, Medizintechnik, Anlagenbau, Luftfahrt und Consumer Goods zu etablieren

Synthesis of LiNi0.5 Mn1.5 O4 cathode materials with different additives: Effects on structural, morphological and electrochemical properties

In this work, LiNi0.5 Mn1.5 O4 spinel type materials have been prepared by spray drying an aqueous solution of acetates and subsequent calcination of the dried precursors. Three different additives, namely polyvinylpyrrolidon (PVP), citric acid and urea have been used and their influences on the structure, morphology and electrochemical performance of the final cathode materials have been examined. Results show that the employed additives increase the purity of the disordered spinel phase and thus lead to higher discharge capacities. By the use of PVP and citric acid, a more stable cycling behavior and a better rate capability are achieved due to the well-controlled secondary particle morphology. Regarding the microstructural changes, flake-like secondary particle morphology has been observed for the use of PVP in the synthesis process, as in former work reported [J. Power Sources, 293, 137 (2015)]. The evolution of this structure is examined in more detail and possible way of formation is proposed

Synthesis of spinel LiNi0.5Mn1.5O4 with secondary plate morphology as cathode material for lithium ion batteries

Spinel LiNi0.5Mn1.5O4 material has been synthesized by a spray drying process and subsequent solid state reaction. Polyvinylpyrrolidone (PVP) is given as additive to the spray drying precursor solution and its effects on structural and electrochemical properties are evaluated. By using PVP in the synthesis process, the obtained sample displays a secondary plate morphology which is consisting of densely arranged primary octahedrally shaped particles. The new cathode material has a lesser degree of impurity phases, a higher discharge capacity, a superior rate capability, and a slightly better cycling performance than the sample synthesized without PVP. In more detail, by the use of PVP the ratio of Mn3+ to Mn4+ in the final product decreases from 20.8 to 9.2%. The initial discharge capacity at 0.1 C exhibits an increase of about 14%. The normalized capacity at 20 C is 84.1% instead of 67.0%. A slightly improved cycling performance with the capacity retention increase from 93.8 to 97.9% could be observed as well

A high-capacity P2 Na2/3Ni1/3Mn2/3O2 cathode material for sodium ion batteries with oxygen activity

Na2/3Ni1/3Mn2/3O2 with a P2 phase is investigated as a cathod material for sodium ion batteries. It delivers a high discharge capacity of 228 mAh g−1 within 1.5–4.5 V in half cells, which is much higher than the theoretical value of 172 mAh g−1. Metal K-edge X-ray absorption near edge spectroscopy results show that the Mn ions remain in 4 + oxidation state during sodiation/desodiation and the charge compensation is due to the Ni2+/Ni4+ redox. Soft X-ray absorption spectroscopy results reveals a gradient in the valence state of Ni ions from bulk to surface for the charged electrode, and a change in the integrated intensity of O K-edge peak after charging, strongly suggesting that part of the charge compensation takes place at the oxygen sites. In addition, the reduction of Mn ions on the surface is observed on the discharged electrode, which indicates that the carbonate-based electrolyte reacts with the cathode material, resulting in a fast capacity drop. By utilizing an ionic liquid (IL) electrolyte (1 M NaTFSI in Pyr14TFSI) to reduce the interfacial reactions, the discharge capacity of ∼200 mAh g−1 is retained

Low-Cost Orthorhombic Nax[FeTi]O4 (x = 1 and 4/3) Compounds as Anode Materials for Sodium-Ion Batteries

Abundant and low-cost sodium, iron, and titanium have great potentials to act as raw materials for large-scale power sources. Here we report the synthesis of novel orthorhombic Nax[FeTi]O4 (x = 1 and 4/3) anode materials by a solid-state reaction method and their electrochemical behaviors in sodium-ion batteries. These materials are able to reversibly insert additional Na+ ions and show very good cycling stabilities. In particular, the Na4/3[FeTi]O4 material can deliver a high reversible capacity of 120 mA h g-1 at 0.1 C, and cyclic voltammetry (CV) investigation proves that there is no phase transformation during testing cycles. The Na[FeTi]O4 material exhibits an even higher initial charge capacity of 181 mA h g-1 at 0.1 C, and in situ X-ray diffraction (XRD) results indicate that Na+ ions behave in topotactic insertion and extraction manners inside this material. Meanwhile, gas evolutions during the initial redox process are analyzed by an operando mass spectrometry technique. The result suggests that the Na[FeTi]O4 material exhibits an enhanced safety

P3 Na0.9Ni0.5Mn0.5O2 Cathode Material for Sodium Ion Batteries

NaxNi0.5Mn0.5O2 (0.5 ≤ x ≤ 1.2)-layered oxides have been prepared and studied as cathode materials in sodium metal cells. The influence of sodium content on the structure and electrochemical performance of NaxNi0.5Mn0.5O2 (0.5 ≤ x ≤ 1.2) have been investigated. When x is between 0.5 and 0.8, the materials crystallize in the P2 phase. For x in the range of 0.9-1.2, novel P3-type materials have been obtained. Of great interest is the P3-type material with the specific composition Na0.9Ni0.5Mn0.5O2 because it can deliver high discharge capacities (141 and 102 mA h g-1 at 10 and 100 mA g-1, respectively). Compared to P2 NaxNi0.5Mn0.5O2 (0.5 ≤ x ≤ 0.8) materials, it exhibits much better cycling stability (78% capacity retention after 500 cycles in the voltage range of 1.5-4.5 V) and an initial Coulombic efficiency of ∼100%, which is more desirable for practical use. In addition, ex situ X-ray absorption near-edge structure spectra reveal that the redox reaction of nickel ions predominantly contributes to the capacity. Operando X-ray diffraction demonstrates reversible phase changes during the charge/discharge. Density functional theory calculations indicate that P3 NaNi0.5Mn0.5O2 shows a low Na+-diffusion barrier of 237 meV. This unexplored class of P3 cathode materials induces new perspectives for the development of layered cathode materials and more energy-dense sodium ion batteries