Research progress and prospect of potassium-ion batteries

Development and utilization of renewable energy sources have gain great progress in recent years, which lead to increasing demands for large scale energy storage systems. Lithium-ion batteries have been widely used in portable electronic devices and electric vehicles. However, with the exploitation of the Earth’s lithium resources, the cost of lithium-ion batteries is gradually increasing. In contrast, the higher terrestrial potassium content promises inexpensive potassium-ion batteries, and the chemical properties of potassium and lithium ions are similar. Meanwhile, the low redox potential of K promises a high working voltage of potassium ion batteries. Thus, potassium-ion batteries have attracted considerable attention as a capable battery technology. However, the large radius of the potassium ion leads to unsatisfactory ion intercalation and extraction behavior during charging and discharging processes, resulting in poor cycling performance, unsatisfactory rate ability, and low capacity. The challenge remains to explore capable electrode materials for potassium-ion batteries to achieve a high energy density and power density. This review summarizes the anode and cathode materials of potassium-ion batteries in recent reports, including the research progress of graphite and other carbon materials, transition metal oxides/sulfides, alloys, and other anode materials, as well as Prussian blue, layered metal oxides, and polyanionic compound cathode materials, which will provide new ideas for developing high-performance potassium-ion batteries. We also discuss the potassium ion storage mechanism in these electrode materials. This review also demonstrates the approaches (nanotechnology, heteroatom doping, carbon coating, composite fabrication) to further improve the electrochemical performance of the cathode and anode. In addition, we point out the key factors for potassium ion batteries performance, such as the design of anode materials, exploitation of novel cathode materials, and optimization of full potassium ion cells fabrication, which would provide new thought for the development of potassium ion batteries with high performances.