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. Extremely durable K-ion batteries with outstanding rate capability and high specific capacity are reported. 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.image