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Zusammenfassung:
The layered manganese oxide cathode materials suffer from the Jahn-Teller effect of the octahedral Mn3+ ions at low potentials and the anionic oxidation triggered structural degradation at high potentials. Introduction of vacancies in the transition metal layer has proved effective in stabilizing the structure at both the high and low potentials. Herein we specially designed vacancy-containing P2-Na-2/3[Zn1/9Mn7/9 square 1/9]O-2 (NZMO-Vac) and vacancy-free P2-Na-2/3[Zn2/9Mn7/9]O-2 (NZMO) to clarify how the vacancies tailor the spinning states of the Mn3+ ions and benefit the structural stability and kinetic performances. The temperature-dependent magnetic suscep-tibility demonstrates the increase of the Jahn-Teller inactive low-spin Mn3+ ions in NZMO-Vac at low potentials. Density functional theory calculations and advanced physical characterizations further indicate that the TM vacancies facilitate the generation of the low-spin Mn3+ ions by decreasing the Mn-O bond length during discharging. These findings provide new ideas on designing cathode materials with higher specific capacities and robust structures.
