An Abnormal 3.7 Volt O3‐Type Sodium‐Ion Battery Cathode |
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| Authors: | Peng‐Fei Wang Hanshen Xin Tong‐Tong Zuo Dr. Qinghao Li Dr. Xinan Yang Dr. Ya‐Xia Yin Prof. Xike Gao Prof. Xiqian Yu Prof. Yu‐Guo Guo |
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| Affiliation: | 1. CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing, P.R. China;2. University of Chinese Academy of Sciences, Beijing, P. R. China;3. Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (CAS), Shanghai, P.R. China;4. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing, P.R. China |
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| Abstract: | Layered O3‐type sodium oxides (NaMO2, M=transition metal) commonly exhibit an O3–P3 phase transition, which occurs at a low redox voltage of about 3 V (vs. Na+/Na) during sodium extraction and insertion, with the result that almost 50 % of their total capacity lies at this low voltage region, and they possess insufficient energy density as cathode materials for sodium‐ion batteries (NIBs). Therefore, development of high‐voltage O3‐type cathodes remains challenging because it is difficult to raise the phase‐transition voltage by reasonable structure modulation. A new example of O3‐type sodium insertion materials is presented for use in NIBs. The designed O3‐type Na0.7Ni0.35Sn0.65O2 material displays a highest redox potential of 3.7 V (vs. Na+/Na) among the reported O3‐type materials based on the Ni2+/Ni3+ couple, by virtue of its increased Ni?O bond ionicity through reduced orbital overlap between transition metals and oxygen within the MO2 slabs. This study provides an orbital‐level understanding of the operating potentials of the nominal redox couples for O3‐NaMO2 cathodes. The strategy described could be used to tailor electrodes for improved performance. |
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| Keywords: | cathodes high voltage O3 phase orbital hybridizations P3 phase |
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