Abstract
In recent years, the rapid growth in the market of electric vehicles has resulted in the increase of prices for lithium, cobalt, and nickel resources used in lithium-ion batteries. Therefore, a great research effort has been conducted to explore new battery systems based on more abundant resources with lower costs. Recently, rechargeable sodium-ion batteries have been attracting much attention for energy storage applications.[1] In this study, Mn-based sodium layered oxide, P'2 Na2/3MnO2 is revisited as a positive electrode material for sodium-ion batteries, and factors affecting its electrochemical performances is examined. The cycle stability of Na2/3MnO2 is remarkably improved by increasing the lower cut-off voltage during cycling. This is because the electrochemical cycling in a higher voltage range maintains a higher average oxidation state of Mn ions in the electrode (i.e., less local distortion induced by Jahn-Teller Mn3+ ions). Furthermore, the use of highly concentrated electrolytes, in which the presence of free solvent molecules is eliminated, effectively suppresses the Mn dissolution, thus enabling stable cycling with >80% capacity retention for more than 1000 cycles. From these results, the possibility of Na2/3MnO2 as a practical positive electrode for sodium-ion battery applications is discussed.Reference[1] T. Sato et al., and N. Yabuuchi, Energy Material Advances, 2021, 9857563 (2021).
Published Version
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