Uniform P2-K0.6CoO2 Microcubes as a High-Energy Cathode Material for Potassium-Ion Batteries

Layered transition-metal (TM) oxides have drawn ever-growing interest as positive electrode materials in potassium-ion batteries (PIBs). Nevertheless, the practical implementation of these positive electrode materials is seriously hampered by their inferior cyclic property and rate performance. Reported here is a self-templating strategy to prepare homogeneous P2-K0.6CoO2 (KCO) microcubes. Benefiting from the unusual microcube architecture, the interface between the electrolyte and the active material is considerably diminished. As a result, the KCO microcubes manifest boosted electrochemical properties for potassium storage including large reversible capacity (87.2 mAh g-1 under 20 mA g-1), superior rate performance, and ultralong cyclic steady (an improved capacity retention of 86.9% under 40 mA g-1 after 1000 cycles). More importantly, the fabrication approach can be effectively extended to prepare other layered TM oxide (P3-K0.5MnO2, P3-K0.5Mn0.8Fe0.2O2, P2-K0.6Co0.67Mn0.33O2, and P2-K0.6Co0.66Mn0.17Ni0.17O2) microcubes and nonlayered TM oxide (KFeO2) microcubes.