With high theoretical capacity and operating voltage, KVPO4F is a potential high energy density cathode material for potassium-ion batteries. However, its performance is usually limited by F loss, poor electronic conductivity, and unsteady electrode/electrolyte interface. Herein, a simple one-step sintering process is developed, where vanadium-oxalate-phosphite/phosphate frameworks and fluorinated polymer are used to synthesize carbon-coated KVPO4F nanoplates. It is found that the V-F-C bond generated by fluorinated-polymer-derived carbon at the interface of KVPO4F/C nanoplates diminishes the F loss, as well as enhances K-ions migration ability and the electronic conductivity of KVPO4F. The as-synthesized KVPO4F/C cathode delivers a reversible capacity of 106.5 mAh g-1 at 0.2 C, a high working voltage of 4.28 V, and a rate capability with capacity of 73.8 mAh g-1 at the ultrahigh current density of 100 C. In addition, a KVPO4F/C//soft carbon full cell exhibits a high energy density of 235.5 Wh kg-1.
Keywords: cathode; fluorophosphate materials; interface engineering; nanostructure; potassium-ion batteries.