Understanding the redox process upon electrochemical cycling of the P2-Na0.78Co1/2Mn1/3Ni1/6O2 electrode material for sodium-ion batteries

Charifa Hakim; Noha Sabi; Le Anh Ma; Mouad Dahbi; Daniel Brandell; Kristina Edström; Laurent C Duda; Ismael Saadoune; Reza Younesi

doi:10.1038/s42004-020-0257-6

Understanding the redox process upon electrochemical cycling of the P2-Na_0.78Co_1/2Mn_1/3Ni_1/6O₂ electrode material for sodium-ion batteries

Commun Chem. 2020 Jan 22;3(1):9. doi: 10.1038/s42004-020-0257-6.

Authors

Charifa Hakim^{1

2}, Noha Sabi^{3

4}, Le Anh Ma⁵, Mouad Dahbi³, Daniel Brandell⁵, Kristina Edström⁵, Laurent C Duda⁶, Ismael Saadoune⁷, Reza Younesi⁵

Affiliations

¹ Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Lot 660-Hay Moulay Rachid, Ben Guerir, Morocco. charifa.hakim@um6p.ma.
² LCME, Faculty of Science and Technology, Cadi Ayyad University, Av. A. El Khattabi, P.B.549, Marrakesh, Morocco. charifa.hakim@um6p.ma.
³ Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Lot 660-Hay Moulay Rachid, Ben Guerir, Morocco.
⁴ LCME, Faculty of Science and Technology, Cadi Ayyad University, Av. A. El Khattabi, P.B.549, Marrakesh, Morocco.
⁵ Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 751 21, Uppsala, Sweden.
⁶ Department of Physics and Astronomy, Division of Molecular and Condensed Matter Physics, Uppsala University, Box 516, 751 20, Uppsala, Sweden.
⁷ LCME, Faculty of Science and Technology, Cadi Ayyad University, Av. A. El Khattabi, P.B.549, Marrakesh, Morocco. I.saadoune@uca.ma.

Abstract

Rechargeable sodium-ion batteries have recently attracted renewed interest as an alternative to Li-ion batteries for electric energy storage applications, because of the low cost and wide availability of sodium resources. Thus, the electrochemical energy storage community has been devoting increased attention to designing new cathode materials for sodium-ion batteries. Here we investigate P2- Na_0.78Co_1/2Mn_1/3Ni_1/6O₂ as a cathode material for sodium ion batteries. The main focus is to understand the mechanism of the electrochemical performance of this material, especially differences observed in redox reactions at high potentials. Between 4.2 V and 4.5 V, the material delivers a reversible capacity which is studied in detail using advanced analytical techniques. In situ X-ray diffraction reveals the reversibility of the P2-type structure of the material. Combined soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering demonstrates that Na deintercalation at high voltages is charge compensated by formation of localized electron holes on oxygen atoms.