Inorganic cathode materials for potassium ion batteries

Potassium ion batteries have attracted much attention in the field of large-scale electrochemical energy storage due to their abundant resources, low cost, performance safety, and environmental non-toxicity. However, drawbacks such as large atomic weight and radius of potassium ion and short cycle life limit its practical application. The performance of cathode materials is a critical factor of the potassium ion battery, which directly affects the battery energy density, cycle life, and safety. Nevertheless, inorganic cathode materials play an important role in the research of potassium ion battery cathode materials. Herein, we review the current development of inorganic cathode materials targeting for the exploration and development of high-performance potassium ion batteries on introducing (i) inorganic cathode materials including Prussian blue and its analogs, layered metal oxides, and polyanionic inorganic materials, (ii) the crystal structure, storage mechanism and modification of electrode materials, (iii) the intrinsic relationship between material composition, structure and electrochemical performance. This review not only is an amalgamation of different viewpoints in reference works but also contains concise perspectives and strategies.