High-performance Na ion cathodes based on the ubiquitous and reversible O redox reaction. Issue 47 (19th September 2018)

• Record Type: Journal Article
• Authors: Assadi, M. Hussein N.; Fronzi, Marco; Ford, Mike; Shigeta, Yasuteru
• Is Part Of: Journal of materials chemistry. Volume 6:Issue 47(2018)
• Page Start: 24120
• Page End: 24127
• Publication Date: 2018-09-19
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8ta05961f
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : We identified high capacity, high voltage and low-strain Na cathode materials that rely on the reversible oxygen redox reaction. Abstract : Utilising reversible oxygen redox in Na and transition metal oxides offers unprecedented opportunities for the design of high voltage, high capacity and affordable cathodes for application in rechargeable Na-ion batteries. Through a judicious materials search and theoretical investigations, we identified new compounds with excellent energy storage properties that rely on oxygen states for charge compensation during the redox reaction. According to our predictions, Na2− x MoO4 demonstrates a voltage of 4.743 V and an energy density of ∼617.3 W h kg −1 . These values exceed the performance of most commercialised Na-ion cathode materials. Furthermore, both Na4− x Zr5 O12, demonstrating a voltage of 3.583 V, and Na1− x Pd2 PO3, demonstrating a voltage of 2.630 V, exhibit a meagre absolute volume change of ∼1% during the sodiation/desodiation process. Because of this minor volume change, these compounds are suitable for all-solid-state battery applications. An examination of the electronic structures of these compounds reveals that O states are always present at the top of the valence band regardless of the presence of 4d transition metal species or their oxidation states. This feature is attributed to the exceedingly substantial 4d–2p hybridisation over the entire valence band which also prevents the bonding of oxidised O ions in the desodiated compounds, thus preventing irreversible oxygen loss.