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成果報告書詳細
管理番号20190000000575
タイトル*2018年度中間年報 革新型蓄電池実用化促進基盤技術開発(国立大学法人三重大学)
公開日2019/6/11
報告書年度2018 - 2018
委託先名国立大学法人三重大学
プロジェクト番号P16001
部署名次世代電池・水素部
和文要約
英文要約Title: Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2) (FY2016-FY2020) FY2018 Annual Report, Mie University, Japan

Nano-interface controlled batteries (halide) are expected to have some advantages such as higher energy density, high input-output characteristics and higher thermal stability. However, fluoride ionic conductors with both high ionic conductivity and wide electrochemical window have not been reported. We focused on oxyfluorides with perovskite (PV)-type structure as a candidate of novel fluoride ion conductors. Most oxyfluorides with PV-type structure are synthesized under high-pressure, while some oxyfluorides are synthesized by an anion exchange reaction. In this research, the synthesis condition of SrFeO2F synthesized by an anion exchange reaction were studied.
SrFeO2.8 as a parent material were sintered at 900 °C and then 1200 °C in air. The oxide obtained was mixed with PVdF as a fluorine source and heated at 400 °C under nitrogen and air flow as reported previously. XRD measurements demonstrated that the sample was obtained as single phase. The reflections shifted to lower angle side than those of the parent oxide. EPMA and EDX analysis confirmed that the sample contained fluorine.
Metal-sulfide cathodes have high theoretical capacity but exhibit poor capacity retention with charge/discharge cycles because of a dissolution of lithium polysulfide species from the active materials. In the case of carbonate electrolyte, the dissolved lithium polysulfides would react quickly with carbonate molecules to form a passivation layer on the cathode surface. Therefore, the cathode surface has to be effectively protected from the dissolved lithium polysulfides. In this project, we applied a polymer thin layer to coat the cathode surface for an improvement of poor cycle performance.
We prepared three types of polyethylene oxide (PEO) network polymer film, cross-linked by heating at around 100 °C or UV irradiation. Vanadium sulfide and other metal-sulfide electrodes coated with the thermally cross-linked polymers showed an improvement of capacity retention. We concluded that thin polymer coatings on the cathodes have a positive effect to suppress cycle deterioration.
To elucidate performance of the polymer layer on the cycle deterioration, coated/uncoated electrodes after charge/discharge tests were observed with SEM. The deposited layer was clearly seen on the uncoated electrode surface. According to the cross-sectional EDX mapping, the layer contained mainly carbon and oxygen atoms probably occurred from the decomposition of electrolyte solutions. However, in the polymer coated electrodes vanadium and fluorine were found in the polymer layer without forming any other deposit layer. The observations suggest that the polymer coating prevents dissolution of active materials into electrolyte solutions and deposition of reaction products on the electrode surface.
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