Enhanced Fast‐Discharging Performance and Cyclability in Oxygen‐Redox‐Based P3‐Type Na‐Layered Cathode via Vacancies in TM layers

Abstract Oxygen redox in layered oxide cathodes for Na‐ion batteries is considered a promising approach for improving the energy density. However, oxygen‐redox‐based cathodes suffer from sluggish kinetics and undesirable structural change during charge/discharge, leading to poor electrochemical performances. Herein, introducing vacancies (□) in the transition metal layers enables the enhanced oxygen redox‐based electrochemical performances in the P3‐type Mn‐based layered oxide cathode is demonstrated. The vacancies can play a role of the local distortion buffers, resulting in the enhanced oxygen redox kinetics and the suppressed structural deformation such as P3‐O3(II) phase transition. The oxygen‐redox‐based P3‐type Na 0.56 [Ni 0.1 Mn 0.81 □ 0.09 ]O 2 exhibits the large discharge capacity of ≈140.95 mAh g −1 at 26 mA g −1 with a high average discharge voltage of ≈3.54 V (vs Na + /Na). Even at 650 mA g −1 , its discharge capacity and average operation voltages delivered ≈122.06 mAh g −1 and ≈3.22 V, respectively. Especially, the small gap of average discharge voltage indicates both improves power‐capability and enhanced kinetics of oxygen redox in P3‐type Na 0.56 [Ni 0.1 Mn 0.81 □ 0.09 ]O 2 . Moreover, the vacancy buffer in the transition metal layers results in the stable cycle‐performance of P3‐type Na 0.56 [Ni 0.1 Mn 0.81 □ 0.09 ]O 2 with the capacity retention of ≈80.80% for 100 cycles, due to the suppressed P3‐O3(II) phase transition.