超高容量かつ低コストの鉄系全固体フッ化物イオン二次電池正極材料の開発

2025-06-20 東京科学大学

図1．本研究で開発したSrFeO₂F_x、Ca_0.8Sr_0.2FeO₂F_x正極と既存正極材料の重量あたりの容量と体積あたりの容量の比較。SrFeO₂F_x、Ca_0.8Sr_0.2FeO₂F_x正極は結晶構造から分子状酸素形成を伴って予想されるよりも多くのフッ化物イオン（x > 1）を可逆的に挿入することで高い容量を示す。

＜関連情報＞

• https://www.isct.ac.jp/ja/news/ky2njku25q5k
• https://www.isct.ac.jp/plugins/cms/component_download_file.php?type=2&pageId=&contentsId=1&contentsDataId=1794&prevId=&key=cccca22e61e54103efaac7516f369e8a.pdf
• https://advanced.onlinelibrary.wiley.com/doi/10.1002/aenm.202406131

フッ化物イオンの過剰な挿入／抽出が可能にするアースアバンダントカソードの超高容量化 Ultra-High-Capacity of Earth-Abundant Cathodes Enabled by Excess Fluoride-Ion Insertion/Extraction

Yanchang Wang, Kentaro Yamamoto, Yuki Sakaguchi, Jun Miyawaki, Toshiyuki Matsunaga, Datong Zhang, Hisao Kiuchi, Zulai Cao, Koji Nakanishi, Toshiki Watanabe, Neha Thakur, Mukesh Kumar …
Advanced Energy Materials  Published: 17 June 2025
DOI:https://doi.org/10.1002/aenm.202406131

Abstract

All-solid-state fluoride-ion batteries (FIBs) are highly prospective candidates for next-generation batteries due to their superior energy density and safety to lithium-ion batteries (LIBs). Nevertheless, the full potential of FIBs remains unrealized, as practical cathode materials remain elusive. Here, a perovskite oxyfluoride SrFeO₂F_x is reported to exhibit topotactic F⁻ (de)intercalation and provide a large capacity of 350 mAh g⁻¹ (1843 mAh cm⁻³) with negligibly small volume expansion (≈0.5%). The large capacity is attributed to excess F⁻ (de)intercalation of ≈2.3 mol in SrFeO₂F_x with Fe²⁺/Fe³⁺ redox and oxygen redox. Furthermore, Sr-substituted CaFeO₂F_x (Ca_0.8Sr_0.2FeO₂F_x) has the highest capacity of 580 mAh g⁻¹ (2595 mAh cm⁻³) among cathode materials using the topotactic ion (de)intercalation, including LIBs. For the first time, the possibility is presented that the utilization of ultimate anion redox associated with the ion (de)intercalation to achieve specific capacities surpassing current active materials by over twofold.