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Revisit of Layered Sodium Manganese Oxide: Achievement of High Energy by Ni Incorporation

Abstract

Sodium-ion batteries (SIBs) have been intensively investigated as a potential alternative to lithium-ion batteries. Among the studied cathodes, the cost-effective P2-type Na2/3MnO2 cathode is particularly attractive because it can deliver high capacity and high energy density. However, its cyclability during prolonged use remains an issue because of the Jahn–Teller distortion associated with the presence of Mn3+. In this study, the effect of Ni doping on the electrochemical properties of Na2/3MnO2 was investigated by varying the Ni content in the range of x = 0–0.2 in Na2/3[Mn1-xNix]O2. Of these materials, Na2/3[Mn0.8Ni0.2]O2 exhibited the best electrochemical performance in terms of capacity and retention as well as improved thermal properties. Although in situ operando synchrotron X-ray diffraction analysis of the structural stability indicated that the Na2/3[Mn0.8Ni0.2]O2 underwent a bi-phasic reaction (a P2–O2 transformation when charged to 4.3 V), the resulting volume change from P2 to O2 was only approximately 10%. This low volume change was possible because of the Ni2+ substitution of partial Mn3+ in the crystal structure, which is thought to have suppressed the cooperative Jahn–Teller distortion, as demonstrated by extended X-ray absorption fine structure analysis. As a result, the post-cycled Na2/3[Mn0.8Ni0.2]O2 was able to maintain its original structure, whereas structural disintegration was observed for Na2/3MnO2. Our findings provide a po-tential new path to utilize cost-effective Mn-rich high-capacity cathode materials for SIBs.

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Publication details

The article was received on 05 Mar 2018, accepted on 06 Apr 2018 and first published on 10 Apr 2018


Article type: Paper
DOI: 10.1039/C8TA02067A
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Revisit of Layered Sodium Manganese Oxide: Achievement of High Energy by Ni Incorporation

    A. Konarov, J. U. Choi, Z. Bakenov and S. Myung, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C8TA02067A

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