Advances and perspectives on transitional metal layered oxides for potassium-ion battery

Potassium-ion batteries are among the most promising candidates to satisfy the large-scale energy storage systems due to their low-cost and abundant potassium sources. However, it is highly desired to seek suitable cathode materials with high capacity and voltage platform, long cycling stability and durability. Transitional metal layered oxides as the most important cathode materials have been widely investigated in lithium-ion batteries and sodium-ion batteries. Recently, transitional metal layered oxides for potassium-ion batteries have aroused huge attention owing to their special structures and potential in applications. Although most transitional metal layered oxides exhibit tolerable capacities, the relationship between structure and electrochemical performance needs further investigation in detail. Herein, the research status and development of transitional metal layered oxides for potassium-ion batteries are summarized in this review. To solve the existing problems of transitional metal layered oxides in potassium-ion batteries, the improvement of air stability and electrochemical performance are also thoroughly discussed. Based on the achievements in recent years, a prospect on the further development of transitional metal layered oxides for potassium-ion batteries is also provided.