Approaching Reactive KFePO4 Phase for Potassium Storage by Adopting an Advanced Design Strategy

Pristine KFePO4 is electrochemically inactive towards potassium, which suggests that K+ ion migration is unfavorable in the KFePO4 structure. Therefore, it is a challenge to create a reactive structure of KFePO4 towards reversible potassium insertion/extraction. In this study, we have fabricated reactive KFePO4 phase by adopting high-energy ball milling technique where tiny nanoparticles (similar to 1.0-1.5 nm) of KFePO4 are created and embedded in the Super P carbon black matrix, which provides conductivity and helps to stabilize the electrode structure. The combination of nano-sizing and the conductive matrix appears to activate electrochemical reactivity. The obtained carbon incorporated KFePO4 material appears to be amorphous. The electrode produces an average operational potential of similar to 2.5 V (vs K+/K) with high capacity retention of 90 mAh g(-1). It is anticipated that this work could pave the way for further studies on cathodes and generate huge attention to the role of ball milling and particle size control on electrochemical activity of KFePO4 materials for the development of PIBs.