Design of active sites in carbon materials for electrochemical potassium storage

Carbon materials have attracted considerable attention as anodes for potassium ion batteries owing to their low-cost, nontoxicity, and controllable structures. The potassium storage behavior of carbon materials is highly associated with their active sites. In recent years, significant advances have been made in designing the active sites of carbon materials to meet the requirements of different potassium-based storage devices. Here, potassium storage mechanisms (intercalation and adsorption) for guiding the rational design of carbon materials are discussed. Based on these mechanisms, the review provides fundamental insight into the relationship between the structures and potassium storage performance of different carbon materials, including graphite, soft carbon, hard carbon, porous carbon, heteroatom-doped carbon, hybridized carbon and composited carbon. The structural design principles of carbon anode materials for potassium-ion full cell and potassium-ion capacitors are summarized based on the initial coulombic efficiency, capacity, potential plateau, rate performance, and cyclic stability. Finally, the problems and future research directions for the design of active sites in carbon materials for electrochemical potassium storage are considered.