high reversible capacity of 273 mAh g −1 , close to the theoretical capacity of 279 mAh g −1 . [9] However, it suffers a significant capacity fading resulting from the large volume change of ≈60% during cycling process. [10,11] And, the rate performance needs to be improved at high current densities because of the poor diffusion kinetics of K + . [12,13] Thus, nongraphitic carbon-based materials prepared by various methods come into the research field of PIB anode. Such as, hard carbon microspheres fabricated by carbonizationetching strategy or hydrothermal reaction combined with pyrolysis method, [14,15] hard-soft composite carbon prepared by combination of hydrothermal reaction with pyrolysis method, [16] graphene prepared with a chemical vapor deposition (CVD) method, [17] graphene aerogel fabricated through Hummers' process combined with hydrothermal treatment process, [18] and carbon nanofiber prepared by a modified oxidative template assembly route following with annealing process. [19] Particularly, carbon nanofibers (CNFs) prepared by electrospinning organic precursor followed with heat treatment has gained great attention. The prepared CNFs possess many unique characteristics, such as flexibility, morphology controllability, and high conductivity, which suggest that the CNFs can be directly used as anode for PIB without binders and carbon-conductive additives, as well as the heavy metal foil. [12,20] In this way, the total specific capacity can be improved comparing with the electrode fabricated by traditional slurry-casting method. [21,22] As previous researches reported, designing specific structures, such as porous structure and hollow structure, is helpful to improve the electrochemical performance of PIB. [23][24][25][26] Porous structure can improve electrochemical performance by not only facilitating ion transport with shortened diffusion distance, but also providing small resistance. [24] For instance, Wan and co-workers have confirmed that hollow structure can facilitate the mass transportation by shorten diffusion pathway and buffer the volume change of anode material during cycling process. [25] Inspired by this, we introduce a unique structure amorphous carbon -multichannel carbon fibers (MCCFs) as freestanding PIB anode to solve the problems PIB suffered including the volume change and poor diffusion kinetics of K + during charge/ discharge process. Namely, on the one hand, the multichannels Potassium-ion battery (PIB) is a potential low-cost energy storage technology owing to the abundant source and wide distribution of potassium element. However, the PIB usually suffers from poor cycling and rate performance induced by volume expansion and sluggish potassiation kinetics. Herein, multichannel carbon fibers (MCCFs) are rationally constructed as freestanding PIB anodes by electrospinning suitable ratio of poly(methyl methacrylate)/polyacrylonitrile with subsequent calcination treatment. The MCCF electrode shows a high reversible capacity/charge capacity of 420.1/304.2 mAh g −1 at current dens...
