High-entropy cathode materials for sodium-ion batteries: Correlating synthesis, crystal structure and electrochemical properties

Abstract

Since the emergence of research on cathode materials for sodium-ion batteries, numerous chemical compositions were investigated as potential promising candidates. Layered transition metal oxides, polyanionic compounds, and Prussian blue analogues are the main reported categories. Their practical use in large-scale applications depends on maintaining good electrochemical properties and high structural/thermal stabilities. High entropy materials have shown great interest by the research community as they were reported to exhibit enhanced electrochemical performance and preserved structural integrity by suppressing or delaying the phase transitions during insertion/de-insertion of Na+ ions.This review presents the crucial role of cathode materials in defining the performance of the overall battery and the encountered challenges and limitations. The concept of high entropy (HE) as well as its advantageous effect on the physico-chemical properties was emphasized. Furthermore, special attention was given to the high entropy cathode materials by correlating their experimental preparation, structural properties, and electrochemical performance in sodium-ion batteries. Finally, the prospects and challenges for developing future HE cathodes were discussed.