Enhanced electrochemical performances and mechanistic understanding of nitrogen-doped porous carbon nanofibers with adjustable porosity for use as freestanding anodes in potassium-ion batteries

Potassium ion batteries (PIB), valued for their abundant resource and low cost, often struggle with the inferior electrochemical performances in conventional anodes. This study explore the use of nitrogen-doped porous carbon nanofibers, featuring diverse pore size distributions, as anode for PIB. We manipulate the porosities of these fibers through a synergetic process of ZnO plasma enhanced atomic layer deposition (PEALD) and carbothermal reduction. The Zcnf30 samples, with their unique nanostructures and surface compositions, show improved electrochemical performances. They deliver a high reversible capacity of 327 mA h g-1 at 50 mA h g-1, sustain a capacity of 86 mA h g-1 at 2 A g-1, and retain a capacity of 120 mA h g-1 after 500 cycles at 1 A g-1. These results are attributed to the increased pyridine and pyrrolic nitrogen content and optimal porous structures, aiding potassium ion absorption and diffusion. Furthermore, the potassium ion storage in the samples involves surface reaction and solid state diffusion-controlled. The majority of the capacity contribution is ascribed to surface reaction, which are pivotal for their high rate performance. The study offers fresh insight into the improved electrochemical performances and the storage mechanism of PIB within nitrogen doped porous carbon nanofibers.