Intensive research on a number of potentially economical potassium-containing host materials as cathode materials for PIB have been reported recently, but most of the potassium-based materials are still not able to meet industrial standards. This mainly stems from the structural instability posed during the electrochemical extraction of the large potassium ion, and also the electrochemical inactivity of some of the host materials. Therefore, at this juncture, it is necessary to identify potassium-containing host materials that can reversibly (de)insert potassium.
During the course of our investigation, we have identified K-rich phosphate-based cathode frameworks that can facilitate reversible (de)insertion of potassium-ion. In this presentation, we will briefly introduce our current research progresses on phosphate-based polyanion cathode materials (such as KxMP2O7 pyrophosphates (some of the phases of which are shown in Fig. 1), KxMPO4F fluorophosphates and KxMPO4 monophosphates (x=1,2)) and provide preliminary results about their electrochemical activity.