Dual stabilization in potassium Prussian blue and cathode/electrolyte interface enables advanced potassium-ion full-cells.

Potassium Prussian Blue (KPB) have been investigated as promising cathode materials for potassium-ion batteries. However, numerous structure defects and side reactions at electrode/electrolyte interface will deteriorate the electrochemical properties. Herein, dual stabilization strategy of structure of KPB particles and cathode/electrolyte interface is reported to enhance the capacity and electrochemical stability. The structure of KPB is stabilized through inhibiting nucleation and growth by addition of ethylenediaminetetraacetic acid dipotassium salt during co-precipitation, which can enlarge the particle size. Meanwhile, stabilizing the cathode/electrolyte interface via changing potassium hexafluorophosphate to potassium bis (fluorosulfonyl) imide (KFSI) electrolyte can further reduce side reactions to boost the coulombic efficiency of KPB cathode. Benefiting from dual engineering in structure of KPB and cathode/electrolyte interface, the half-cell in KFSI electrolyte possesses two discharge potential plateaus at 3.4 and 4.0 V with reversible capacity of 92.7 mAh g-1 at 0.03 A g-1. To demonstrate its practical use, KPB//graphite full-cell device is successfully constructed, exhibiting the capacity up to 102.4 mAh g-1 at 0.1 A g-1, high-rate (40.4 mAh g-1 at 1.5 A g-1) and superior cyclic stability (88% capacity retention from cycle 25 to 400 at 1 A g-1). This work provides a synergetic engineering strategy to realize the powerful application of high-performance potassium-ion full-cell devices in energy storage.