context: Recently, potassium manganese oxides (KMOs) have gained more attention as positive materials due to their high operating voltage, high conductivity and controllable flexible interlayer spacing, which are beneficial for K+ ion diffusion and offer more ion intercalation channels over the whole exposed surface. For example, Kim et al. reported a P3-type layered structure of K0.5MnO2 as the cathode material for non-aqueous potassium-ion batteries, which exhibited a specific capacity of ≈100 mA h g−1 with good capacity retention. Zhao et al. synthesized AlF3-coated K1.39Mn3O6 microspheres that showed a highly reversible capacity of 110 mA h g−1 at 10 mA g−1, excellent cycling stability and rate capability. Xia et al. prepared the high K-content K0.77MnO2·0.23H2O for high-performance non-aqueous K-ion batteries with 134 mA h g−1 at a current density of 100 mA g−1.
answer: K0.5MnO2