Open Access

Show Abstract ▼

Abstract: Ni-rich layered oxides, like NCM-811, are promising lithium-ion battery cathode materials for applications such as electric vehicles. However, pronounced capacity fading, especially at high voltages, still lead to a limited cycle life, whereby the underlying degradation mechanisms, e.g. whether they are detrimental reactions in the bulk or at the surface, are still controversially discussed. Here, we investigate the capacity fading of NCM-811/graphite full-cells over 1000 cycles by a combination of in situ synchrotron X-ray powder diffraction, impedance spectroscopy, and X-ray photoelectron spectroscopy. In order to focus on the NCM-811 material, we excluded Li loss at the anode by pre-lithiating the graphite. We were able to find a quantitative correlation between NCM-811 lattice parameters and capacity fading. Our results prove that there are no considerable changes in the bulk structure, which could be responsible for the observed ≈20% capacity loss over the 1000 cycles. However, we identified the formation of a resistive surface layer, which is responsible for (i) an irreversible loss of capacity due to the material lost for its formation, and (ii) for a considerable impedance growth. Further evidence is provided that the surface layer is gradually formed around the primary NCM-811 particles.

Show Abstract ▼

Abstract: We demonstrate the pressure-induced formation of supercrystals made from PEGylated gold nanorods in aqueous suspension. Utilizing the combined effect of hydrostatic pressure and salt on the solubility of the organic PEG shell that passivates the nanorods, the reversible formation of two-dimensional hexagonal supercrystals has been observed by means of small angle X-ray scattering. The pressure dependence of the crystal lattice's structural parameters is determined. By time-resolved measurements performed after a pressure-jump, the growth process of the crystals is found to be finished already after a few seconds. The presented results demonstrate that by PEGylating nanoparticles pressure-induced homogeneous supercrystals can be formed for different particle shapes, in particular anisotropic nanorods, which determine the resulting lattice type.

Show Abstract ▼

Abstract: Potassium-ion (K-ion) batteries potentially offer numerous advantages over conventional lithium-ion batteries as a result of the high natural abundance of potassium and its lower positive charge density, compared with lithium. This introduces the possibility of using K-ion in fast charging applications, in which cost effectiveness is also a major factor. Unlike for sodium-ion batteries, graphite can be used as an anode in K-ion cells, for which an extensive supply chain, electrode manufacturing infrastructure, and knowledge already exists. However, the performance of graphite anodes in K-ion cells does not meet expectations, with rapid capacity fading and poor first cycle irreversible capacities often reported. Here we investigate the formation and composition of the solid electrolyte interphase (SEI) as well as K+ insertion in graphite anodes in K-ion batteries. Through the use of energy-tuned synchrotron-based X-ray photoelectron spectroscopy, we make a detailed analysis at three probing depths up to ~50 nm of graphite anodes cycled to various potentials on the first discharge-charge cycle. Extensive SEI formation from a KPF6/DEC:EC electrolyte system is found to occur at low potentials during the insertion of potassium into graphite. During the subsequent removal of potassium from the structure, the thick SEI is partially stripped from the electrode, demonstrating that the SEI layer is unstable and contributes to a significant proportion of the capacity on both discharge and charge. With this in mind, further work is required to develop an electrolyte system with stable SEI layer formation on graphite in order to advance K-ion battery technology.

Show Abstract ▼

Abstract: d‐Amino acids are the “wrong” enantiomers of amino acids as they are not used in proteins synthesis but evolved in selected functions. On this side, d‐aspartate (d‐Asp) plays several significant roles in mammals, especially as an agonist of N‐methyl‐d‐aspartate receptors (NMDAR), and is involved in relevant diseases, such as schizophrenia and Alzheimer's disease. In vivo modulation of d‐Asp levels represents an intriguing task to cope with such pathological states. As little is known about d‐Asp synthesis, the only option for modulating the levels is via degradation, which is due to the flavoenzyme d‐aspartate oxidase (DASPO). Here we present the first three‐dimensional structure of a DASPO enzyme (from human) which belongs to the d‐amino acid oxidase family. Notably, human DASPO differs from human d‐amino acid oxidase (attributed to d‐serine degradation, the main coagonist of NMDAR) showing peculiar structural features (a specific active site charge distribution), oligomeric state and kinetic mechanism, and a higher FAD affinity and activity. These results provide useful insights into the structure‐function relationships of human DASPO: modulating its activity represents now a feasible novel therapeutic target.

Show Abstract ▼

Abstract: The production of lignin nanoparticles (LNPs) has opened new routes to utilization of lignin in advanced applications. The existing challenge, however, is to develop a production method that can easily be adapted on an industrial scale. In this study, we demonstrated a green and rapid method of preparing LNPs directly from a sulfur-free alkaline pulping liquor by combining acid-precipitation and ultrasonication. The combined method produced spherical LNPs, with hierarchical nanostructure and highly negative surface charge, within only 5-min of sonication. The mild, rapid sonication was achieved by sonicating directly without prior drying the acid-precipitated and dialyzed lignin. Optimization of the method revealed the potential for minimizingacid consumption, shortening the dialysis time, and processing directly the alkaline liquor with as much as 20 wt% lignin. The isolated LNPs were stable during storage for 180 days, at a pH range of 4–7 and in a dispersing medium below 0.1 M NaCl. The LNPs also displayed excellent emulsifying properties, stabilizing oil-in-water emulsions. Thus, this simple and energy-efficient method opens a sustainable, straightforward and scalable route to production of solvent-free LNPs, with high potential as interface stabilizers of multi-phase systems in the food and medical industries.