Local spring effect in titanium-based layered oxides

Heng Su; Gencai Guo; Yang Ren; Xiqian Yu; Xu Zhang; Tianyuan Ma; Yue Lu; Zihe Zhang; Hao Ma; Manling Sui; Hong Li; Chengjun Sun; Zonghai Chen; Guiliang Xu; Ruzhi Wang; Khalil Amine; Haijun Yu

doi:10.1039/D0EE02313B

Local spring effect in titanium-based layered oxides†

Heng Su,‡^ab Gencai Guo,‡^a Yang Ren,

^c Xiqian Yu,

^d Xu Zhang,

^a Tianyuan Ma,^b Yue Lu,^e Zihe Zhang,^a Hao Ma,^a Manling Sui,^e Hong Li,

^d Chengjun Sun,^c Zonghai Chen,^b Guiliang Xu,^b Ruzhi Wang,

*^a Khalil Amine

*^bfg and Haijun Yu

*^a

Author affiliations

* Corresponding authors

^a Faculty of Materials and Manufacturing, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, P. R. China
E-mail: hj-yu@bjut.edu.cn, wrz@bjut.edu.cn

^b Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
E-mail: amine@anl.gov

^c X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA

^d Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese academy of Sciences, Beijing, China

^e Institute of Solid State Microstructure and Properties, Beijing University of Technology, Pingleyuan #100, Chaoyang District, Beijing 100124, China

^f Department of Material Science and Engineering, Stanford University, Stanford, CA 94305, USA

^g Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University (IAU), Dammam, Saudi Arabia

Abstract

Titanium-based layered oxides (TLOs) are one of the most promising electrode material families for sodium-ion batteries (NIBs) due to their smooth charge/discharge profiles and excellent cycle performance. However, the reaction mechanism of these materials, especially the reason for the disappearance of multiple voltage plateaus, is still not clear. Herein, two representative TLOs (Na_2/3Ni_1/3Ti_2/3O₂ and Na_2/3Co_1/3Ti_2/3O₂) with the same P2 crystal structure have been studied to scrutinize those unexplained issues. In situ synchrotron high-energy X-ray diffraction revealed a solid solution reaction mechanism for both, suggesting the absence of rigid phase transitions upon electrochemical cycling. An interesting “spring effect” of the TiO₆ octahedron, i.e., the reversible vibration of the central Ti atom inside the local octahedron upon electrochemical redox, was demonstrated by advanced X-ray absorption spectroscopy and theoretical calculations. Such an effect could suppress the rigid phase transitions, and result in smooth charge/discharge profiles and enhanced cycle stability. This work not only accounts for the disappearance of multiple voltage plateaus of TLOs for NIBs, but also provides an effective local-structure viewpoint to increase the cycle stability of electrode materials for other advanced battery systems.

Energy & Environmental Science

Local spring effect in titanium-based layered oxides†

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Local spring effect in titanium-based layered oxides

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