Effect of Cu Substitution in P′2- and P2-Type Sodium Manganese-Based Oxides

Layered manganese oxides have been considerably studied toward sustainable sodium-ion battery materials. There has a focus on the specific roles of Cu as member substituents in sodium oxides. Herein, effects substitution for Mn P′2- and P2-type Na0.67[CuxMn1–x]O2 (0 ≤ x 0.33) are systematically investigated, focusing cooperative Jahn–Teller distortion Mn3+ Cu2+ ions. Na0.67[Cu0.2Mn0.8]O2 is selected to gain further insights oxygen redox along with Na0.67[Cu0.1Mg0.1Mn0.8]O2 Na0.67[Cu0.1Zn0.1Mn0.8]O2. Comparative studies among three materials reveal that type substituent(s) no impact activation redox. In contrast, nature concentration substituted element(s) influence structural evolution during charge/discharge. Na0.67[Cu0.2Mn0.8O2] maintains P2 phase without any secondary at bulk local scales end charge 4.5 V, leading suppressed voltage hysteresis. At discharge 1.5 presence higher results distorted P′2 degree 10.6(1)%. This can induce large lattice stress related mismatch between P′2, which jeopardizes cyclability.