Tohoku University · 공학
Kohei Shimokawa 교수의 연구실은 주로 마그네슘 이온 배터리의 핵심 과제인 고체 전극의 안정성 향상과 전해질 설계에 중점을 두고 있다. 산화물 기반 양극에서의 마그네슘 이온의 불안정한 상전이와 산화막 형성을 방지하기 위해 스파이널 구조의 안정화 및 고체 전해질의 농도 최적화를 통한 마그네슘 금속의 부식 방지 기술을 개발하고 있다. 또한 광전기 재충전 기반의 고전압 양극 소재 개발과 고속 주행 가능한 고체-액체 복합 양극의 자가 생성 메커니즘 등 미래형 에너지 저장 장치의 실현 가능성을 탐색하고 있다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
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)<sub>2</sub>/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 MgCl<sub>2</sub> salt can be dissolved in concentrated Mg(TFSA)<sub>2</sub>/G3 solutions, and the passivation of Mg metal is markedly suppressed in such highly concent
Photocharging of high-potential spinel LiMn<sub>2</sub>O<sub>4</sub> is demonstrated by using a water-in-salt electrolyte and TiO<sub>2</sub> nanoparticles. In a developed half-cell system with an electron acceptor, Li extraction from LiMn<sub>2</sub>O<sub>4</sub> proceeds under the illumination of UV-visible light at an estimated rate of ∼23 mA g<sup>-1</sup>. 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<sub>1.5</sub>M<sub>0.5</sub>O<sub>4</sub> (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<sub>1.5</sub>Fe<sub>0.5</sub>O<sub>4</sub> 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
