Anion redox reactions offer a means of enhancing the capacity of layered sodium transition metal oxide positive electrode materials. However, oxygen redox reactions typically show limited reversibility and irreversible structural...
Sodium layered oxides showing oxygen redox activity are promising positive electrodes for sodium-ion batteries (SIBs). However, structural degradation typically results in limited reversibility of the oxygen redox activity. Herein, the effect of Zn-doping on the electrochemical properties of P3-type sodium manganese oxide, synthesised under air and oxygen is investigated for the first time. Air-Na 0.67 Mn 0.9 Zn 0.1 O 2 and Oxy-Na 0.67 Mn 0.9 Zn 0.1 O 2 exhibit stable cycling performance between 1.8 and 3.8 V, each maintaining 96 % of their initial capacity after 30 cycles, where Mn 3 + /Mn 4 + redox dominates. Increasing the voltage range to 1.8-4.3 V activates oxygen redox. For the material synthesised under air, oxygen redox activity is based on Zn, with limited reversibility. The additional transition metal vacancies in the material synthesised under oxygen result in enhanced oxygen redox reversibility with small voltage hysteresis. These results may assist the development of high-capacity and structurally stable oxygen redox-based materials for SIBs.
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