Na2Ru0.8Mn0.2O3: A novel cathode material for ultrafast sodium ion battery with large capacity and superlong cycle life

Sodium ion batteries have attracted special research interests world widely for large-scale electrical stationary applications due to the abundant reserve and wide distribution of Na element. However, most cathodes suffer from limited capacity, poor rate capability or inferior cycling stability, which cannot meet the requirements of high-performance sodium ion batteries. Thus, developing cathode materials with improved capacity, rate and cycling performance is in urgent demand. Herein, we design a series of Na2Ru1-xMnxO3 using both cationic and anionic redox activities to achieve high capacity. Mn-doped Na2RuO3 has been found to be capable of enhancing the oxygen redox activity, raising the redox potential, preventing the generation of spinel phase and moisturesensitive phase upon charge process, facilitating charge transfer kinetics and suppressing the O3 -> P3 phase transition in a long cycle. As a result, Na2Ru0.8Mn0.2O3 exhibits outstanding electrochemical performance by delivering a large capacity of over 90 mAh g(-1) for long cycling of 1000 times at a high rate of 5 C. This study provides a prototype of high-performance ion-doped Na-rich cathode and could encourage scientists to explore more Na2MM'O-3 materials for ultrafast sodium ion batteries with large capacity and superlong cycle life.