Active material and interphase structures governing performance in sodium and potassium ion batteries

Development of energy storage systems is a topic of broad societal and economic relevance, and lithium ion batteries (LIBs) are currently the most advanced electrochemical energy storage systems. However, concerns on the scarcity of lithium sources and consequently the expected price increase have driven the development of alternative energy storage systems beyond LIBs. In the search for sustainable and cost-effective technologies, sodium ion batteries (SIBs) and potassium ion batteries (PIBs) have attracted considerable attention. Here, a comprehensive review of ongoing studies on electrode materials for SIBs and PIBs is provided in comparison to those for LIBs, which include layered oxides, polyanion compounds and Prussian blue analogues for positive electrode materials, and carbon-based and alloy materials for negative electrode materials. The importance of the crystal structure for electrode materials is discussed with an emphasis placed on intrinsic and dynamic structural properties and electrochemistry associated with alkali metal ions. The key challenges for electrode materials as well as the interface/interphase between the electrolyte and electrode materials, and the corresponding strategies are also examined. The discussion and insights presented in this review can serve as a guide regarding where future investigations of SIBs and PIBs will be directed.

The importance of the active material structure and the interface/interphase between the electrode and electrolyte in enhancing the electrochemical performance of sodium and potassium ion batteries.     

Dispersion of stratum corneum in an aqueous mixed solution of surfactants: the effect of a mixture of sodium dodecyl sulfate and N,N-dimethyldodecylamine oxide

Molecular interactions between sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine oxide (C₁₂DMAO), whose mixtures were effective for dispersion of stratum corneum (SC) into intact corneocytes, were studied and found to be strongest at an SDS/C₁₂DMAO molar ratio of 1/3, when dispersion of SC was most effective and the sizes of the mixed micelles were largest.

This dispersion effect was confirmed as being caused by the stronger solubilizing power of molecular complexes formed between SDS and C₁₂DMAO in the binary mixed solutions by using ¹H NMR. The mechanisms for removing intercellular lipids such as ceramides, cholesterol and their derivatives, which play an important role as adhesives among the corneocytes, and for dispersing SC into intact cells were proposed on the basis of supporting data obtained from ¹H-NMR and light scattering measurements.     

A novel peptide synthesis using fluorous chemistry

Three new fluorous supports for peptide synthesis, i.e., the trialkoxybenzhydryl-type (6), the Wang-type (7) and the tert-butyl-type support (8), were prepared. A bioactive peptide TRH was easily synthesized by an Fmoc strategy using the benzhydryl-type fluorous support with fluorous chemistry.     

Absolute rate constants for the coordination of olefins to a transient coordinatively unsaturated cobalt complex

Absolute second-order rate constants for the coordination of diethyl phenylphosphonite and various olefins to a transient coordinatively unsaturated cobalt complex, i.e. hydridotris(diethyl phenylphosphonite)cobalt(I), have been measured in cyclohexane at 23° C using laser flash photolysis techniques. The rate constants have been found to depend markedly on the structures of the olefins, e.g. 1.2 × 10⁸ and 6.5 × 10⁴M^?1 s^?1 for 1-hexene and tetramethylethylene, respectively. The mechanism of photochemical double-bond migration catalyzed by the transient is discussed on the basis of these rate constants.     

Vinyl polymerization. 432. Initiation mechanism of uncatalyzed polymerization in the presence of copper(II) ion

The initiation mechanisms of the uncatalyzed polymerization of methyl acrylate and methyl methacrylate by the system of starch, α-amylase or water-soluble nylon 3/copper(II) ion/H₂O were investigated by spin trapping techniques. Using 2,4-dimethyl-3-nitrosobenzene sulfonate d₈ and 5,5-dimethyl-1-pyrroline-N-oxide as the water-soluble spin trapping agents, the simultaneous generation of both monomer and hydroxyl radicals has been observed, and the propriety of the initiation mechanism proposed previously was confirmed. Thus, the initiation of polymerization in the presence of copper(II) ion was concluded to take place through a hydrogen atom transfer from the complexed water to the β-carbon of the complexed monomer.     

Rapid oligosaccharide synthesis on a fluorous support

The novel fluorous support Hfb (hexakisfluorous chain-type butanoyl) was easily prepared. The Hfb group was readily introduced into the anomeric hydroxyl group of a carbohydrate, and was recyclable after cleavage. The use of the Hfb group was applicable for the rapid oligosaccharide synthesis in which the synthetic intermediates could be purified using fluorous and normal organic solvents. Each synthetic intermediate could be monitored by TLC, NMR and mass spectrometry.     

Data-aquisition system for cyclic voltammetry at a microelectrode and application to fast electrode kinetics

A data-aquisition system for fast micro-electrode voltammetry is described. The computer-controlled system can be used at scan rates up to 10 000 V s^?1. The response of the system was examined by monitoring fast electrochemical reactions. A heterogeneous rate constant of 1.1 cm s^?1 was obtained for oxidation of ferrocene in acetonitrile. Oxidation of anthracene in acetonitrile was also studied; the enthalpy of activation was evaluated as 13 kJ mol^?1 for the reaction of the anthracene radical cation with acetonitrile.     

Addendum to ``Dense subsets of the boundary of a Coxeter system'

In this paper, we investigate boundaries of parabolic subgroups of Coxeter groups. Let be a Coxeter system and let be a subset of such that the parabolic subgroup is infinite. Then we show that if a certain set is quasi-dense in , then is dense in the boundary of the Coxeter system , where is the boundary of .

     

Realization of transient memory-loss with NiO-based resistive switching device

A resistive switching device based on a nickel-rich nickel oxide thin film, which exhibits inherent learning and memory-loss abilities, is reported in this work. The conductance of the device gradually increases and finally saturates with the number of voltage pulses (or voltage sweepings), which is analogous to the behavior of the short-term and long-term memory in the human brain. Furthermore, the number of the voltage pulses (or sweeping cycles) required to achieve a given conductance state increases with the interval between two consecutive voltage pulses (or sweeping cycles), which is attributed to the heat diffusion in the material of the conductive filaments formed in the nickel oxide thin film. The phenomenon resembles the behavior of the human brain, i.e., forgetting starts immediately after an impression, a larger interval of the impressions leads to more memory loss, thus the memorization needs more impressions to enhance.