Mn and Co co-doped perovskite fluorides KNiF₃ with enhanced capacitive performance

Perovskite-based aqueous supercapacitors have important development prospects due to their advantages of high energy density, low cost, environmental benignity. Here, bimetallic Ni-Mn and trimetallic Ni-Co-Mn perovskite fluorides are prepared via facile solvothermal method and characterized as positive electrode materials for supercapacitors. The structure, composition, chemical states and the electrochemical properties of these samples are investigated in detail. Three electrode measurements indicate that the electrochemical properties of the perovskite fluorides KNiF₃ depend on the nature and amount of dopants. Partial doping of Ni by Mn increases the rate capability but decreases the specific capacity, while Co and Mn co-doping improve both the rate capability and specific capacity of perovskite fluoride KNiF₃. The K-Ni-Co-Mn-F (Ni/Co/Mn = 12:2:1) sample exhibits the maximum specific capacity of 211 mAh g^-1, low internal resistance and a high rate capability (82% capacity retention from 1 to 16 A g^-1). Furthermore, the AC//K-Ni-Co-Mn-F (Ni/Co/Mn = 12:2:1) asymmetric supercapacitor delivers a maximum energy density of 50.2 Wh kg^-1. These results prove that Co and Mn co-doped KNiF₃ can be a promising material for supercapacitor.