P3-type K0.5Mn0.72Ni0.15Co0.13O2 microspheres as cathode materials for high performance potassium-ion batteries

Potassium ion batteries (PIBs) have been considered as promising candidates for large-scale energy storage due to their high operating voltage and low cost. Nevertheless, the inferior cycling stability and rate capability of cathode materials hinder their practical applications. Herein, we synthesized P3-type K0.5Mn0.72Ni0.15Co0.13O2 microspheres with high tap density as cathode materials for PIBs through solvent-thermal method. The as-prepared materials are densely packed secondary microspheres that consist of submicron-sized primary particles. The unique hierarchical structure can not only effectively facilitate potassium-ion transport owing to short diffusion distance, but also withstand high stress that caused by continuous K+ intercalation/deintercalation. As a result, when tested as cathode materials for PIBs, P3-type K0.5Mn0.72Ni0.15Co0.13O2 microspheres deliver a reversible capacity of 82.5 mA h g(-1) at 10 mA g(-1), superior rate capability with a capacity of 57.9 mA h g(-1) at 500 mA g(-1), and excellent cycling stability with 85% capacity retention after 100 cycles at 50 mA g(-1). Even cycled at 200 mA g(-1), it still maintains 75% capacity retention after 300 cycles. Moreover, P3-type K0.5Mn0.72Ni0.15Co0.13O2 microspheres with high tap density can increase compaction density of electrode, and thus obtain a high volumetric energy density of 121.1 W h L-1 based on the cathode electrode volume. This study provides a feasible way to develop high energy density PIBs with excellent cycling stability and rate capability.