Uniform P2-KCoO 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-KCoO (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 under 20 mA g), superior rate performance, and ultralong cyclic steady (an improved capacity retention of 86.9% under 40 mA g after 1000 cycles). More importantly, the fabrication approach can be effectively extended to prepare other layered TM oxide (P3-KMnO, P3-KMnFeO, P2-KCoMnO, and P2-KCoMnNiO) microcubes and nonlayered TM oxide (KFeO) microcubes.