Uniform P2-K 0.6 CoO 2 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-K 0.6 CoO 2 (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-K 0.5 MnO 2 , P3-K 0.5 Mn 0.8 Fe 0.2 O 2 , P2-K 0.6 Co 0.67 Mn 0.33 O 2 , and P2-K 0.6 Co 0.66 Mn 0.17 Ni 0.17 O 2 ) microcubes and nonlayered TM oxide (KFeO 2 ) microcubes.