Role of cation disorder and oxygen redox on voltage and capacity of NaxRuO3 as Na ion battery cathode

讲座名称: Role of cation disorder and oxygen redox on voltage and capacity of NaxRuO3 as Na ion battery cathode
讲座时间 2018-03-12
讲座地点 西安交通大学北二楼11楼会议室
讲座人 Mohammad Hussein Naseef AL ASSADI
讲座名称:Role of cation disorder and oxygen redox on voltage and capacity of NaxRuO3 as Na ion battery cathode
讲座人:Mohammad Hussein Naseef AL ASSADI
讲座摘要:Technologies such as long-range electric vehicles [1] and megawatt storage for renewable energy sources [2] demand high performance batteries. The conventional paradigm based on Li ions as ionic charge carrier faces severe limitations as Li resources are scarce and unevenly distributed throughout the globe [3]. Alternatively, utilizing Na ions instead of Li is promising, however, not without challenges [4]. Na has larger ionic radius and smaller ionization potential compared to Li, lowering the energy density in Na based cathodes [5]. To bring the Na ion based cathodes to that of Li’s level, all performance enhancing auxiliary mechanisms must be carefully fine-tuned. These mechanisms include a new-type of reversible oxide ion redox [6] that increases the capacity and cation disorder that improves the ionic mobility [7].
In this work through density functional calculations, we examine oxygen’s participation in redox reaction in two polymorphs of NaxRuO3. In both hexagonal ( R3m) and monoclinic (C2/m) NaxRuO3, the availability of O electrons for redox reaction originates from the local coordination environment. When O ions are coordinated by four or five Na ions, their 2p electrons are lifted closer to the Fermi level. This orbital rearrangement increases the capacity beyond that of single electron of the transition metal redox and facilitates extra Na extraction. Furthermore, we did not detect any Ru migration in both phases through the desodiation process. This trend indicates structural integrity and good cyclability for both polymorphs. The calculated voltage for cation disordered hexagonal ( R3m) phase was 2.35 V which higher than that of cation ordered monoclinic phase (C2/m) which was 2.21 V.
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[5] C. Liu, Z. G. Neale and G. Cao, Materials Today, 19, 109 (2016).
[6] M. Sathiya, et. al, Nat. Mater., 12, 827 (2013); D.-H. Seo, et al., Nat. Chem., 8, 692 (2016).
[7] Aziz Abdellahi, et al., Chem. Mater., 28, 3659 (2016).



Dr. Mohammad Hussein Naseef AL ASSADI received his PhD in Materials Science and Engineering from the University of New South Wales, Sydney, Australia. He is currently an assistant professor in the School of Physics, University of Tsukuba, Japan. His current research interests are doping and defects in oxides; high throughput computational materials discovery, magnetism and topological effects; thermoelectric effects in oxides and energy storage materials. 

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