Kohei Shimokawa

Development of metal-anode rechargeable batteries is a challenging issue. Especially, magnesium rechargeable batteries are promising in that Mg metal can be free from dendrite formation upon charging. However, in case of oxide cathode materials, inserted magnesium tends to form MgO-like rocksalt clusters in a parent phase even with another structure, which causes poor cyclability. Here, a design concept of high-performance cathode materials is shown, based on: i) selecting an element to destabil

Stabilizing spinel structures with Zn preferring a tetrahedral environment significantly improves the reversibility of the spinel–rocksalt transition with Mg insertion/extraction.

Mg(TFSA)₂/triglyme(G3)-based electrolytes (TFSA: bis (trifluoromethanesulfonyl) amide) are one of candidates for magnesium rechargeable batteries, but the passivation of Mg-metal anode due to the TFSA anion is fatal in practical use. In this work we show that at elevated temperatures around 150 °C a comparable amount of MgCl₂ salt can be dissolved in concentrated Mg(TFSA)₂/G3 solutions, and the passivation of Mg metal is markedly suppressed in such highly concent

Photocharging of high-potential spinel LiMn₂O₄ is demonstrated by using a water-in-salt electrolyte and TiO₂ nanoparticles. In a developed half-cell system with an electron acceptor, Li extraction from LiMn₂O₄ proceeds under the illumination of UV-visible light at an estimated rate of ∼23 mA g^-1. This work paves the way for high-potential cathode materials in photo-rechargeable batteries.

Liquid S/sulfide composite cathodes can be spontaneously synthesized by electrochemically oxidizing sulfides, enabling high-rate magnesium rechargeable batteries.

A study was carried out for the direct spectrophotometric determination of chromium(VI) extracted into organic phase. The method consists of tributyl phosphate (TBP) extraction and spectrophotometry with diphenylcarbazide(DPC), and the established procedure is as follows. Take 100ml of sample solution, containing chromium(VI) less than 20μg, into a separating funnel and add 2 ml of hydrochloric acid. Extract chromium(VI) with 10 ml of TBP by shaking for 5 min. After separation of both phases, tr

A study was carried out on the pathway and the trend of mercury pollution of bottom sediments of the Suimon River. It was difficult to establish the actual mercury pollution level of sediment only with a data of mercury content of sediment because measured values of mercury fluctuated intensely even in an identical sampling station. Then, the triangular coordinate chart method was applied to compare the pictures of mercury pollution among different sampling stations and the years of mercury meas

Mn-based spinel-oxide cathode materials are promising for achieving high-energy-density rechargeable Mg batteries (RMBs). However, Mg insertion into them often induces unfavorable phase transformation due to the poor stability of λ-MnO2, leading to capacity fading during cycling. Defect spinel ZnMnO3, which can be regarded as ZnO-stabilized λ-MnO2, is an outstanding exception that allows highly reversible Mg insertion/extraction. To further understand its phase stability, here we investigate wid

Recently the amounts of various kinds of wastes have increased, as the industrial production has increased and the living standard has elevated in our country. Consequently, the environmental pollutions have advanced all over the country. In an investigation of the environmental pollution, aquatic sediments are found to be useful because hazardous substances are often adsorbed and concentrated in sediments. Perhaps heavy metals are most extensively studied in hazardous substances. In this review

Spinel oxides are promising for high-potential cathode materials of photo-rechargeable batteries. However, LiMn_1.5M_0.5O₄ (M = Mn) shows a rapid degradation during charge/discharge under the illumination of UV-visible light. Here, we investigate various spinel-oxide materials by modifying the composition (M = Fe, Co, Ni, Zn) to demonstrate photocharging in a water-in-salt aqueous electrolyte. LiMn_1.5Fe_0.5O₄ exhibited a substantiall

Cation-exchange capacity (CEC), ignition loss, clay fraction and heavy metal content were measured in bottom sediments from the Nagara River, and the data were subjected to multiple regression analysis. The average CEC of sediments in the middle and lower reach of the river were 3.23 and 10.5 meq/100 g respectively. Good correlations were found between CEC and ignition loss or clay fraction, and multiple correlation coefficients were more than 0.92 among them. From regression equations it was po