Cutting-edge advances for the positive electrode in aqueous K-ion batteries: exploring electrochemical properties, structural designs, and applicable perspectives

Aqueous K-ion batteries (AKIBs) are a promising technology for large-scale energy storage due to their low cost and high safety. However, their positive electrode materials face many challenges, such as structural degradation due to the large K⁺ radius, poor cycling performance and low efficiency, which restrict practical applications. This review provides an overview of the cutting-edge advances of positive electrode materials for AKIBs, highlights the electrochemical properties, modification strategies and structural design of positive electrode materials such as Prussian blue analogs, layered transition metal oxides, polyanionic compounds and MXenes, and discusses the reaction mechanisms of various positive electrode materials. Also explored are (i) the advantages of metal chalcogenides, a new positive electrode material, and (ii) application prospects of high-performance AKIB positive electrode materials to allow the realization of more efficient and stable AKIBs.