Fe-doped layered P3-type K0.45Mn1−xFexO2 (x ≤ 0.5) as cathode materials for low-cost potassium-ion batteries

Abstract A series of iron-substituted layered P3-type manganese oxides, K0.45Mn1−xFexO2 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) were fabricated using a convenient solid-state method and studied as cathode materials for potassium-ion batteries. The microstructure and morphology of the as-synthesized materials were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The electrochemical characteristics of K0.45Mn1−xFexO2 samples have been investigated systematically and K0.45Mn0.8Fe0.2O2 shows the best cyclic stability and highest rate performance. It delivers a large reversible discharge capacity of 106.2 mAh g−1 at 20 mA g−1 with a capacity retention rate of 77.3% after 100 cycles. It also presents obviously enhanced rate performance with the capacity of 64.9 mAh g−1 at 200 mA g−1 and stable cycling capability of 44.7 mAh g−1 after 100 cycles. The results demonstrate that the relatively small substitution (20%) at the transition metal site can improve the cycle stability during potassium ions insertion and extraction. Therefore, the layered P3-K0.45Mn0.8Fe0.2O2 possibly serves as a potentially promising cathode material that made from completely earth-abundant elements for potassium-ion batteries applications.