Sodium layered oxide cathodes: challenges and advances

Teofilo Rojo

CIC Energigune

 Abstract: Currently, there is considerable interest in sodium-ion batteries as they represent a potentially low-cost, more plentiful alternative to increasingly scarce and expensive lithium[1–3]. Here we present an overview of sodium cathode materials, and compare some examples of the leading families.

Sodium layered oxides have a diverse range of phases and stoichiometries, making them very versatile systems. Indeed, by careful control of the constituents it is possible to synthesise materials with high voltages, though this mostly requires elements (e.g. nickel and cobalt) with other, less desirable properties (e.g. high toxicity, high cost, scarcity, etc.). Thus, we will examine this important family in detail, relating their stoichiometry to not only their electrochemical performance, but also to these other important parameters.

In this way, it is possible to demonstrate the importance of sodium manganese-based layered oxides - a result of their good combination of attractive properties (e.g. readily available precursors, low cost, relatively environmentally friendly, etc.). Consequently, these materials will be scrutinized with respect to the relevance of the manganese oxidation state to electrochemistry and several key compounds. We will also show how, through transition metal doping/substitution, it is possible to obtain excellent electrochemical performance without sacrificing their positive properties.

These results will then be summarized and discussed, particularly with respect to full-cell configurations. Finally, based upon this understanding, we will draw conclusions about both the current state of the field, and where future research may be most fruitfully directed.

Biography: Prof. Teófilo Rojo has been Full Professor of Inorganic Chemistry at the University of the Basque Country (UPV-EHU) since 1992 and Scientific Director of CIC energiGUNE since 2010. His research is focused on the study of materials for advanced batteries (lithium, sodium, redox, etc.). He is co-author of more than 500 articles in “peer reviewed” journals with more than 12000 time cites and an h-index of 52. He is co-author of twelve book chapters, co-editor of two books, and he led more than 50 projects (regional, national and European). He also has seven patents related to magnetic and energy materials and has supervised twenty-five Ph.D. students.
Prof. Rojo has been awarded with Research Award of the Spanish Royal Society of Chemistry in the Area of Inorganic (2013), appointed as an Academic Member of the Royal Spanish Academy of Exacts, Physical and Natural Sciences (2015) and TangAoQing Honorary Professorship at Jilin University, China (2016). Among his scientific responsibilities at international level, he is member of the Executive Committee of the Division of Chemistry of solid state and materials (DSSMC) from EuCheMS from 2013 and member of the Working Party on Chemistry and Energy of EuCheMS (European Chemical Science), European Association for scientific discussion in all fields of chemistry related to energy applications, from 2016.