Nanorod Arrays and Advanced Thin Film Materials for High Performance Lithium-Ion Batteries:
Increasing demand for compact and light-weight power sources with high energy and power densities from consumer electronics has triggered the search for alternate materials for use as intercalation hosts in lithium ion batteries. Various thin film deposition techniques are currently used for the preparation of both metal oxide and carbon based electrodes for lithium ion batteries. These are particularly interesting when envisaged for microbattery applications where both the anode and cathode are fabricated as thin films.
In acollaborative project with Dr. Bingwing Wei at University of Delaware, amorphous carbon films and nanorods (Fig. 1) were deposited successfully on Cu foils by our GLAD sputtering technique in our labs and their electrochemical performance as lithium battery anode was studied. The deposited films were extensively characterized using XRD, SEM, AFM and step profilometer for the structural and surface properties. The hydrogen content of the synthesized films was studied using residual gas analysis (RGA). Electrochemical performance was evaluated across Li metal at 0.2 C rate in a non-aqueous electrolyte. The electrochemical performance of the carbon films show unusually low irreversible capacity in the first cycle with a reversible capacity of ~ 810 mAh/g, which is at least 2 times higher than that of conventional graphitic carbon. For the first time in literature, we reported an amorphous carbon showing such a high reversibility in the first cycle, which is very much limited to the graphitic carbon. Predominantly, the low hydrogen content and the low specific surface area of the synthesized amorphous carbon film are considered responsible for such a high first cycle columbic efficiency. The growth mechanism and the reasons for enhanced electrochemical performance of our carbon coatings were also investigated.