Activating abnormal capacity in stoichiometric NaVO3 as cathode material for sodium-ion battery

• Published in: Journal of power sources Vol. 400; pp. 377 - 382
• Main Authors: Zhang, Jiaolong, Su, Bizhe, Kitajou, Ayuko, Fujita, Manabu, Cui, Yunlin, Oda, Mami, Zhou, Wenchong, Sit, Patrick H.-L., Yu, Denis Y.W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-10-2018
• Subjects: Cathode; Density functional theorem; NaVO3; Oxygen-redox reaction; Sodium-ion battery; Sodium-ion battery; Oxygen-redox reaction; Cathode; NaVO3; Density functional theorem
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2018.08.042

Traditional sodium-ion battery cathodes utilize the change in oxidation state of the transition metal(s) in the structure to accommodate the electron transfer during charge and discharge. Recent researches on sodium-rich compounds such as Na2RuO3 and Na2IrO3 suggest that anionic reaction with oxygen can be an additional source of electrons during electrochemical reactions. Here we demonstrate for the first time that stoichiometric NaVO3, despite the valence of vanadium of 5+, delivers a reversible capacity by activating it beyond 4.5 V. Elemental analysis confirms Na removal and insertion from/into NaVO3 during charge/discharge. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy results show that the oxidation state of vanadium remains unchanged, while oxygen is likely to compensate for the charge transfer during charge/discharge. Theoretical calculation on spin density of electrons in the lattice also supports the involvement of oxygen during sodium removal. Our demonstration of the unique behaviors of NaVO3 provides a new exciting direction for research in sodium-ion battery cathodes.
•NaVO3 can be charged despite vanadium in its highest oxidation state.•Capacity of NaVO3 depends strongly on particle size and electrical conductivity.•NaVO3 undergoes reversible charge-discharge after activation.•NaVO3 maintains its crystal structure upon charge and discharge.•Theoretical calculation suggests the involvement of oxygen during sodium removal.