Single-crystalline Mn-based oxide as a high-rate and long-life cathode material for potassium-ion battery

Mn-based oxides are promising cathode materials for potassium-ion batteries due to their high theoretical capacity and abundant raw materials. However, the anisotropic properties of their conventional polycrystalline structures lead to insufficient rate capability and cycle life. Here, a single-crystal Mn-based layered oxide, P3'-type K0.35Mn0.8Fe0.1Cu0.1O2 (KMFCO), is designed and synthesized through a bimetallic co-induction effect and used as a cathode for potassium-ion battery. Benefiting from a unique single-crystal structure that is devoid of grain boundaries, it achieves a higher K+ transport rate and a reduced volume change during the K+ intercalation/ deintercalation process. Accordingly, the single-crystal P3'-type KMFCO delivers superior rate capability (52.9 mAh g-1 at 1000 mA g-1) and excellent cycling stability (91.1% capacity retention after 500 cycles at 500 mA g-1). A full cell assembled with the P3'-type KMFCO cathode and a graphite anode also exhibits a high reversible capacity (81.2 mAh g-1 at 100 mA g-1) and excellent cycling performance (97% capacity retention after 300 cycles). The strategy of developing single-crystal materials may offer a new pathway for maintaining structural stability and improving the rate capability of layered manganese oxide cathodes and beyond.