Single Wall Carbon Nanotube-Containing PVA Based Carbon Nanofibers for Lithium Ion Battery Anodes

Abstract

Lithium ion batteries have increasing importance due to the urgent demand for widespread applications in electric/hybrid vehicles, electronic devices, and the grid energy storage. Graphite is one of the most commonly used anode material with low theoretical capacity(372mAh/g) and limited rate capability. In order to improve battery Li-ion storage capacity many researchers have investigated different carbonaceous anode materials with various configurations. Among them, carbon nanofiber is of particular interest for providing high capacity and cycling stability due to its high surface area, porous structure and high electric conductivity which not only shorten the lithium ion path through the electrode but also provide large electrode/electrolyte interface for the charge-transfer reaction properties. Carbon nanofibers can be directly used as free standing and binder free anodes. There are several nanofiber production methods, among which electrospinning is the most promising due to its simplicity and versatility. Carbon nanofibers can be produced with different precursors such as Pitch, polyacrylonitrile(PAN), polyvinypyrrolidone(PVP), polyvinyl alcohol(PVA) etc. Polyvinyl alcohol is a promising material due to its water soluble and environmentally friendly character. In this study we report a method to produce free-standing binder free single wall carbon nanotube containing carbon nanofibers as anode for lithium ion battery. Composite nanofibers prepared via electrospinning of single wall carbon nanotubes (SWCNT) dispersed into polyvinyl alcohol solution, followed by iodination at 100°C and heat treatment in an inert atmosphere at 800°C. Carbon nanotubes were added to the polymer solution in different concentrations 0,1% , 1%, and 5 %. An increase of the carbon nanotube concentration in the fibers led to carbonized nanofiber mats with increased electrical conductivity. TGA and Raman analyses showed that carbon nanotubes presence improves the carbon yield of the mats and their handleability. Galvanostatic cycling tests of half cells revealed that addition of carbon nanotubes improves battery capacity. We attribute the capacity increase of the composite nanofibers to the carbon nanotubes structure. Moreover carbon nanotubes increased the handleabilitiy of the mat which is crucial for freestanding, binder free anode materials.