Designing carbon anodes for advanced potassium-ion batteries: Materials, modifications, and mechanisms

Recently, the limited abundance and uneven geographical distribution of Li resources seriously hamper the growing demand for lithium-based energy storage devices. In this regard, potassium-ion batteries (KIBs) sharing similar “rocking chair” working principles with lithium-ion batteries have started to attract increasing attention due to their high energy density and abundant potassium resources. Carbon material is considered to show great potential for using as high-performance anode in KIBs. However, it is still a challenge to simultaneously achieve satisfactory specific gravimetric and volumetric capacities, high initial Coulombic efficiency, superior rate performance, and excellent cycle stability due to the sluggish reaction kinetics of the large-sized K-ions. Herein, we summarize the latest research achievements of different types of carbon anodes for KIBs, including graphite, graphene, hard carbon, soft carbon, and carbon nanotubes, in which the key factors affecting the electrochemical performance are explored. Importantly, the alternative strategies for addressing the low gravimetric/volumetric capacity and low initial Coulombic efficiency of carbons are thoroughly emphasized. Finally, the critical issues, challenges, and perspectives are proposed to show the development direction of KIBs. We hope this review can provide researchers with new ideas to design high-performance carbon materials and give insightful perspectives to accelerate the application of carbon electrodes for KIBs.