An Efficient Approach for Quantifying the Mechanical Degradation of Ni‐Rich NMC‐based Cathodes for Lithium‐Ion Batteries using Nano‐XCT Analysis

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An Efficient Approach for Quantifying the Mechanical Degradation of Ni-Rich NMC-based Cathodes for Lithium-Ion Batteries using Nano-XCT Analysis

Nano-XCT analysis for batteries: This study compares scanning electron microscopy images and nano X-ray computed tomography scans of pristine and cycle-aged battery electrodes. Structural changes over the cycle life are determined, and a quantitative analysis of the active material‘s gray scale value distribution reveals severe degradation near the separator interface, with a reciprocal relationship to particle radius.


Abstract

LiNi0.8Co0.1Mn0.1O2 has emerged as a promising electrode material for automotive lithium-ion batteries due to its high specific discharge capacity, cost-effectiveness, and reduced cobalt content. However, despite all mentioned beneficial attributes, the widespread adoption of this material class is impeded by active material degradation during cycling operation, which is linked to performance loss. This study compares scanning electron microscopy images and nano X-ray computed tomography scans with a 3D reconstruction of pristine and cycle-aged battery electrodes to determine structural changes over cycle life. Although a very moderate current rate was chosen for the cycle test, which suggests a homogeneous load across the entire electrode, particle fracture varied across electrode thickness and particle size. A quantitative analysis of the active material‘s gray scale value distribution reveals severe degradation near the separator interface with a reciprocal relationship to particle radius. Remarkably, particle shape and size remain relatively unchanged despite cracking, eliminating the need to adjust these parameters in aging simulations. Moreover, it underscores the practical significance of particle cracking, as it can significantly impact the electrode‘s performance. Thus, analyzing changes in particle shape and size alone is insufficient, and a comprehensive exploration of the particle interior using nano-XCT is necessary.

Why DFT‐Based Tight Binding Gives a Better Representation of the Potential at Metal‐Solution Interfaces than DFT Does

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Why DFT-Based Tight Binding Gives a Better Representation of the Potential at Metal-Solution Interfaces than DFT Does

The inner potential φ experienced by an ion differs greatly from the average electrostatic potential as calculated by DFT. The problem is caused by the divergence of the potential at the sites of the nuclei. DFT-based tight binding gives results in line with values estimated from experiment or from other models, and allows a uniform quantum-mechanical modeling of electrode and solution.


Abstract

In modelling electrochemical interfaces it is important to treat electrode and electrolyte at the same level of theory. Density functional theory, which is usually the method of choice, suffers from a distinct disadvantage: The inner potential is calculated as the average of the total electrostatic potential. This includes the highly localized potential generated from the nuclei. The resulting inner potential is far too high, of the order of 3.5 V, and not relevant for electrochemistry. In the density functional based tight binding (DFTB) method the electrostatic potential is much smoother, as it stems from atomic charge fluctuations with respect to neutral reference atoms. The resulting values for the electrochemical inner potential are much lower and compare well with those obtained by other, elaborate methods. Thus DFTB recommends itself as a method for treating the electrochemical interface including the inner potential.

Heterogeneous Photocatalysts for Light‐Mediated Reversible Deactivation Radical Polymerization

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Heterogeneous Photocatalysts for Light-Mediated Reversible Deactivation Radical Polymerization

Heterogeneous photocatalysis can increase the sustainability of photochemistry by providing simple means for catalyst recovery and reuse. This review explores four prevalent classes of these materials: Photocatalytic Nanoparticles, polymer networks, metal organic frameworks (MOFs), and immobilized photocatalysts on solid supports in their use for light-mediated reversible deactivation radical polymerization.


Abstract

Heterogeneous photocatalysis combines the benefits of light-mediated chemistry with that of a catalytic platform that facilitates re-use of (often expensive) photocatalysts. This provides significant opportunities towards more economical, sustainable, safe, and user-friendly chemical syntheses of both small and macromolecular compounds. This contribution outlines recent developments in the design of heterogenous photocatalysts and their use to mediate polymerizations. We outline four classes of heterogeneous photocatalysts in detail: Nanoparticles, conjugated and non-conjugated polymer networks, metal-organic frameworks (MOFs), and functionalized solid supports.

Halide Complexes of 5,6‐Dicyano‐2,1,3‐Benzoselenadiazole with 1:4 Stoichiometry: Cooperativity between Chalcogen and Hydrogen Bonding

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The [M4–Hal]– (M = the title compound; Hal = Cl, Br, and I) complexes were isolated in the form of salts of [Et4N]+ cation and characterized by XRD, NMR, UV-Vis, DFT, QTAIM, EDD, and EDA. Their stoichiometry is caused by a cooperative interplay of σ-hole-driven chalcogen (ChB) and hydrogen (HB) bondings. In the crystal, [M4–Hal]– are connected by the π-hole-driven ChB; overall, each [Hal]– is six-coordinated. In the ChB, the electrostatic interaction dominates over orbital and dispersion interactions. In UV-Vis spectra of the M + [Hal]– solutions, ChB-typical and [Hal]–-dependent charge-transfer bands are present; they reflect orbital interactions and allow identification of the individual [Hal]–. However, the structural situation in the solutions is not entirely clear. Particularly, the UV-Vis spectra of the solutions are different from the solid-state spectra of the [Et4N]+[M4–Hal]–; very tentatively, species in the solutions are assigned [M–Hal]–. It is supposed that the formation of the [M4–Hal]– proceeds during the crystallization of the [Et4N]+[M4–Hal]–. Overall, M can be considered as a chromogenic receptor and prototype sensor of [Hal]–. The findings are also useful for crystal engineering and supramolecular chemistry.

DOCK 6: Incorporating hierarchical traversal through precomputed ligand conformations to enable large‐scale docking

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DOCK 6: Incorporating hierarchical traversal through precomputed ligand conformations to enable large-scale docking

Molecular docking is a prevalent tool in drug discovery. DOCK 6's extensible design enables implementing and testing new methods in molecular docking. Development in DOCK 3 enabled screening of large databases of billions of small molecules. To allow access to this unprecedented chemical space, we have implemented features from DOCK 3.7 into DOCK 6, including traversal of precomputed ligand conformations stored in a hierarchical database. We test these new features retrospectively.


Abstract

To allow DOCK 6 access to unprecedented chemical space for screening billions of small molecules, we have implemented features from DOCK 3.7 into DOCK 6, including a search routine that traverses precomputed ligand conformations stored in a hierarchical database. We tested them on the DUDE-Z and SB2012 test sets. The hierarchical database search routine is 16 times faster than anchor-and-grow. However, the ability of hierarchical database search to reproduce the experimental pose is 16% worse than that of anchor-and-grow. The enrichment performance is on average similar, but DOCK 3.7 has better enrichment than DOCK 6, and DOCK 6 is on average 1.7 times slower. However, with post-docking torsion minimization, DOCK 6 surpasses DOCK 3.7. A large-scale virtual screen is performed with DOCK 6 on 23 million fragment molecules. We use current features in DOCK 6 to complement hierarchical database calculations, including torsion minimization, which is not available in DOCK 3.7.

The challenge of ab initio calculations of small neon clusters

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Weakly bound neon dimer, trimer and tetramers are studied at HF and CCSD(T) levels using Dunning, ANO and SIGMA-s basis sets. Their ground-state binding energies are studied along with some structural properties. SIGMA-s basis sets have been developed explicitly for this issue but in a manner that can be readily applied to other atoms for the study of larger weakly bound systems. The difficulties for attaining accurate results on these systems are assessed by the computation of total, atomization and correlation energies, as well as equilibrium distances, with several basis sets of increasing size, ranging from non-augmented to double-augmented versions. Extrapolations are proposed to predict stabilization energies and the results are compared with previously published data.