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. [ABSTRACT FROM AUTHOR]