Hierarchical porous nanofibers comprising N-doped graphitic C and ZIF-8 derived hollow N-doped C nanocages for long-life K-ion battery anodes

Abstract

Hierarchical porous carbon nanofibers (NFs) are designed via electrospinning, followed by simple carbonization, and applied as the anode for K-ion batteries (KIBs). The carbonization process is optimized to simultaneously satisfy sufficient graphitization of polyacrylonitrile (PAN)-derived soft carbon and complete conversion of zeolitic imidazolate framework-8 (ZIF-8) to hollow N-doped C nanocages. The prepared NFs through an optimized carbonization consists of porous and hollow N-doped C nanocages, which are encapsulated within the conductive graphitic carbon (GC) matrix, that acts as an efficient electron transport pathway. Moreover, the interconnected porous and hollow nanocages ensure a high contact area between the electrode and electrolyte and reduces the K-ion diffusion length. The N-doped GC with high electrical conductivity in the structure demonstrates reinforcing structural integrity as well as providing additional transport pathways for the unique electron transport. Therefore, the hierarchical porous carbon NFs show outstanding energy storage properties, such as stable cycle performance up to 10,000 cycles at the high current density of 1.0 A g-1 with high areal loading mass (1.8–1.9 mg cm−2) of the active material, which clearly suggests the structural advantages of the nanostructure introduced in this study.