Flexible centrifugally spun PVP based SnO₂@carbon nanofiber electrodes

Sodium-ion batteries (SIBs) have attracted significant attention because of the abundant resource and low-cost of sodium. Furthermore, flexible and wearable functional electronics have been presented as one of the most important emerging technology. Carbon nanofibers are promising candidates for flexible electrodes due to their high electronic conductivity and high surface area, while it is vital to use non-petroleum-based polymers considering environmental concerns. Developing flexible nanostructured electrodes by using environment friendly polymers with a fast and low-cost technique is critical to develop high performance flexible electronics. Electrochemical properties are influenced by the morphology and average fiber diameters of nanofibers. In this study, poly(vinylpyrrolidone) (PVP) solutions with various concentrations and two different solvent systems (ethanol/water and ethanol/dimethylformamide) were successfully spun into nanofibers by the fast, safe, low-cost, and environment friendly technique of centrifugal spinning. The effect of solvent system and solution concentration was investigated by using scanning electron microscopy images, and the average fiber diameters varied from 436 nm to 3 µm. Moreover, nine different heat treatments were studied, and the effect of time and temperature during stabilization and carbonization on the morphology of carbon nanofibers (CNFs) was investigated. Furthermore, flexible carbon nanofibers were fabricated and used as binder-free anodes in sodium-ion batteries. In order to enhance the electrochemical properties of flexible CNFs, flexible SnO₂@CNFs were fabricated by combining centrifugal spinning and heat treatment. The electrochemical performance of the flexible SnO₂@carbon nanofiber anodes was evaluated by conducting galvanostatic charge/discharge tests and cycling voltammetry. A high rate of performance was also presented. The high reversible capacity of 400 mA h/g was delivered when flexible centrifugally spun PVP based SnO₂@carbon nanofiber electrodes were used in SIBs.