Durable K-ion batteries with 100% capacity retention up to 40,000 cycles

Currently, the major challenge in terms of research on K-ion batteries is to ensure that they possess satisfactory cycle stability and specific capacity, especially in terms of the intrinsically sluggish kinetics induced by the large radius of K + ions. Here, we explore high-performance K-ion half/full batteries with high rate capability, high specific capacity, and extremely durable cycle stability based on carbon nanosheets with tailored N dopants, which can alleviate the change of volume, increase electronic conductivity, and enhance the K + ion adsorption. The as-assembled K-ion half-batteries show an excellent rate capability of 468 mA h g −1 at 100 mA g −1 , which is superior to those of most carbon materials reported to date. Moreover, the as-assembled half-cells have an outstanding life span, running 40,000 cycles over 8 months with a specific capacity retention of 100% at a high current density of 2000 mA g −1 , and the target full cells deliver a high reversible specific capacity of 146 mA h g −1 after 2000 cycles over 2 months, with a specific capacity retention of 113% at a high current density of 500 mA g −1 , both of which are state of the art in the field of K-ion batteries. This study might provide some insights into and potential avenues for exploration of advanced K-ion batteries with durable stability for practical applications.