Effect of Iodination Temperature on the Polyvinyl Alcohol Based Carbon Nanofiber for Lithium Ion Battery Anodes

Abstract

Nanofibers has broad application areas including energy, filtration, biomedical and many other engineering fields due to their high porosity, high surface area to volume ratio. Researchers studied several materials and production methods in order to obtain different superior properties from nanofibers. Recently, lithium ion batteries has achieved huge importance due to growing demand for portable electronics, electric vehicles and grid energy storage,etc. Batteries have different components among them anodes have crucial importance on the battery capacity, cycle life and rate capability. One of the promising 1D anode material as carbon nanofibers can provide fast electron transport, reduced lithium ion diffusion lenghts and enhanced surface area comparing to commercial electrodes. There are several carbon nanofiber precursors, such as polyacrylonitril(PAN), lignin, pitch, polyimide(PI).. etc. among them polyvynil alcohol has important advantage because of their environmentally friendly, water soluble and low cost properties. Polyvinyl alcohol (PVA) is a water-soluble polyhydroxy polymer with a broad range of industrial and technical applications. It has been used as a carbon precursor or directly used as anode, cathode or separator in Li-ion batteries. PVA based carbon nanofibers can be easily obtained by electrospinning and subsequent carbonization PVA might be an environmentally friendly alternative material for PAN based carbon fibers. However rather than oxidative stabilization in PAN based precursors, linear PVA chains must be stabilized via other suitable processes. There are various routes that have been proposed to suppress the thermal degradation of PVA before carbonization step, such as using HCl, H2SO4, NH4 vapour or chemical impregnation into different salts. Stabilization of PVA under iodine vapour is a promising approach with high carbon yield for obtaining carbon nanofibers. In this study, we investigated the effect of iodination temperature on the morphology, chemical structure, and electrical properties of carbon nanofiber webs fabricated from electrospun PVA nanofibers. Obtained nanofibers were subjected to different iodination temperature and then converted into carbon nanofibers. It was found that increasing the iodination temperature provides higher carbon yield. Carbon nanofibers were used as binder free, self- standing anode for lithium ion battery. Battery performances showed that PVA based carbon nanofibers are promising anode materials for lithium ion batteries.