Triggering hollow carbon nanotubes via dual doping for fast pseudocapacitive potassium-ion storage

Heteroatom doping is effective to adjust the active site, ion transportation and electronic transfer in carbonaceous materials for electrochemical energy storage. Herein, we report hollow carbon nanotubes (HCNT) co-doped with boron and nitrogen for fast potassium-ion storage. With the doping level of (B = 13.4 at.%, N = 14.3 at.%), HCNT anodes display unique performance merits: large specific capacity (383 mA h g−1 at 0.02 A g−1), enhanced rate capability (189 mA h g−1 even at 1.0 A g−1) and improved cycling stability (capacity remaining 70% after 500 cycles at 1.0 A g−1). In-situ Raman and ex-situ morphology investigations demonstrate a highly reversible evolution in G and D bands of HCNT and confirm the sturdy structure for highly reversible potassium ion storage. Further electrochemical kinetics analyses reveal the dominated capacitive potassium-storage process with a high average K+ diffusion coefficient. These findings enrich the understanding of the heteroatom doping engineering in carbons for potassium-ion batteries.