2025-07-17 東京理科大学,東京科学大学
図 β-NaMnO2の走査透過電子顕微鏡像と結晶構造のモデル図
（左）積層欠陥有りのβ-NaMnO2、（右）積層欠陥無しのβ-NaMnO2（高分解能電子顕微鏡像は㈱住化分析センターにて取得）
＜関連情報＞
- https://www.tus.ac.jp/today/archive/20250711_6689.html
- https://advanced.onlinelibrary.wiley.com/doi/10.1002/adma.202507011
積層欠陥のないβ-NaMnO2の合成と電気化学特性 Synthesis and Electrochemistry of Stacking Fault-Free β-NaMnO2
Shinichi Kumakura, Kei Kubota, Syuhei Sato, Yusuke Miura, Huu Duc Luong, Eun Jeong Kim, Yoshinobu Miyazaki, Tomohiro Saito, Yoshitaka Tateyama, Shinichi Komaba
Advanced Materials Published: 14 July 2025
DOI:https://doi.org/10.1002/adma.202507011
Abstract
Understanding the solid-state chemistry of corrugated layered sodium manganese oxide (β-NaMnO2) has been hindered by stacking faults (SFs), particularly in the presence of α-type planar domains among β-type corrugated MnO2 layers. Thus, their prospects as cathode materials for Na-ion batteries have never been assessed comprehensively. The partial substitution of Cu for the Mn in β-NaMnO2 yields SF-free β-phase, as confirmed via atomic scale scanning transmission electron microscopy. The SF-free material enables the identification of unique phase transitions during electrochemical Na extraction/insertion, showing drastic gliding of the corrugated layers. The proposed gliding mechanism is validated both experimentally, using ex situ synchrotron X-ray diffraction, and theoretically, through density functional theory calculations. Minor structural changes observed in SF-containing materials indicated that gliding is extremely sensitive to SFs. Given that the SF-free β-material exhibits excellent cycle stability in a Na cell, the corrugated layer is concluded to have high resilience and reversibility against repeated large anisotropic structural changes involving slab gliding, providing a new insight into the design of long-life rechargeable batteries.
