Efficient pathways to improve electrode performance of P′2 Na2/3MnO2 for sodium batteries

Abstract

A Mn-based sodium-containing layered oxide, P′2-type Na_2/3MnO₂, is revisited as a positive electrode material for sodium-ion batteries, and factors affecting its electrochemical performances are examined. The cyclability of Na_2/3MnO₂ is remarkably improved by increasing the lower cut-off voltage during cycling even though the reversible capacity is sacrificed. Furthermore, the use of highly concentrated electrolytes, in which the presence of free solvent molecules is eliminated, effectively suppresses the dissolution of Mn ions, thus enabling stable cycling with >85% capacity retention for 300 continuous cycles.