Facile fabrication of polyacrylonitrile-based carbon nanofibers with multimodal channel using polycaprolactone as sacrificial polymer for boosting ion transfer

Heterogeneous pore structure such as geometric shape, size, spatial distribution, and interconnectivity in carbon materials determines the absorption/desorption, diffusion, and migration of electrolyte ions at the electrode/electrolyte interfaces, which significantly influence supercapacitor (SC) performance. Therefore, engineering carbon nanofibers (CNFs) to trade-off the capacitive performance and porous structure of carbon materials remains intriguing. Herein, a blend of polycaprolactone (PCL) with polyacrylonitrile (PAN), as CNFs precursor, was investigated to evaluate the feasibility of PCL as sacrificial polymer, one of the commercially available biodegradable polymers, for the design and fabrication of multimodal channel architecture. The PAN/PCL blend with different weight ratios of 7:3, 5:5, and 3:7 were dissolved in N,N-dimethylformamide (DMF) and electrospun to prepare PAN/PCL composite nanofibers, followed by heat treatment such as stabilization and carbonization. As-prepared CNFs displayed the hierarchical pore structure with abundant multi-channels along the nanofiber axis, which promotes electrolyte ion transport. Especially, the carbonized PAN/PCL55 sample revealed the best electrochemical performance of 162 F g⁻¹ at 10 A g⁻¹ among all CNFs prepared from PAN/PCL composite nanofibers. This outcome was attributed to the phase separation mechanism between PAN and PCL in binary blend by DMF used as a co-solvent as well as the heteroatom doping (N and O) of the active sites formed by PCL pyrolysis. In conclusion, this work provides a feasible and practical method for high performance and low-cost substrate to compensate for low capacitance of CNFs, which has an impact on the design of porous structure for advanced electrode in SCs.