P2-type Na0.6[Mg(II)0.3Mn(IV)0.7]O2 as a new model material for anionic redox reaction

A new model material of Na_0.6Mg(Ⅱ)_0.3Mn(IV)_0.7]O₂, with only Mg²⁺ and Mn⁴⁺ in the transition metal layers, is synthesized for the research of anionic redox reaction. The material delivers a capacity of~130 mAh/g with a long plateau at~4.2 V in the initial charge profile, indicating anionic redox reaction (ARR) involved during the initial desodiation process. In the following cycles, the reversible capacity can reach a high value of~210 mAh/g, which is probably derived from the participation of both ARR and Mn³⁺/Mn⁴⁺ redox couples, further proving the charge compensation from ARR during the initial charge and following cycles. The designed cathode material without Mn³⁺ helps avoid the influence of oxygen activity from transition metals, enabling the investigation of ARR without other distractions.