Electrode performance of P′2-Na2/3[Mn1-xScx]O2 in sodium batteries

Abstract

P′2-Na_2/3MnO₂ is one of the promising candidates of high-capacity positive electrode material showing >200 mAh g⁻¹ for Na-ion batteries. However, it suffers capacity decay during electrochemical cycling. In this study, we used Sc³⁺ ions ([Ar]4s⁰3d⁰) as a dopant for P′2-Na_2/3MnO₂ and successfully synthesized series of doped materials, P′2-Na_2/3[Mn_1-xSc_x]O₂. Electrochemical cycle stability of the Sc doped samples in Na cells is successfully improved by the doping without sacrificing reversible capacity. Since Sc³⁺ ion having no 3d-electrons can be partially substituted for Jahn-Teller active Mn³⁺ ions ([Ar]4s⁰3d⁴), loss of the crystallinity over cycling is mitigated through suppressing the structural transformation including Na/vacancy ordering. The finding provides the insight to design the long-life layered cathode materials for Na-ion batteries.