Highly wrinkled carbon tubes as an advanced anode for K-ion full batteries

Potassium ion batteries (KIBs) have attracted tremendous attention due to their low cost, appropriate redox potential, and abundance of source materials. Although the intercalation of potassium ions into graphite has been demonstrated to be feasible, the electrochemical performance of graphite in KIBs remains hampered and it is still challenging to achieve sufficiently high energy storage. In this work, nitrogen/oxygen dualdoped highly wrinkled carbon tubes (NO-WCTs) are rationally designed based on a novel two-step wrinkle formation mechanism for the first time as an attempt to overcome the challenge. The asobtained NO-WCTs constructed through an in situ solid-state approach possess a wrinkled morphology, few-layer hollow microstructure, and effective heteroatom modifications, leading to both ultrahigh capacity (ca. 536 mA h g 1) and excellent cycling stability (92.8% capacity retention at 3 A g 1 even after 2000 cycles); these are some of the best capabilities yet reported for carbonaceous electrode materials in KIBs and can be ascribed to the enhanced diffusion kinetics and sufficient K-ion penetration as a result of the enlarged surface, shortened K-ion diffusion distance, and effective N/O co-doping. Particularly noteworthy, the unique NO-WCTs also exhibit remarkable potassium storage capability in practical K-ion full batteries using P3 phase K0.69CrO2 as the cathode with impressive cycling stability over 500 cycles even at 1C rate.