Ball Milled Si-W Alloy Anode Materials for Lithium Ion Batteries

Abstract

Si-based materials are excellent alternatives to conventional graphite anodes because of their high theoretical capacity and high earth abundance. This thesis explores the electrochemical and structural characteristics of Si-W alloy anode materials prepared by ball milling. X-Ray diffraction was used to characterize the microstructure of the Si-W alloys and for quantitative phase characterization during the ball milling process. Analysis of phase behavior allowed for a model to be developed to explain the milling process. Electrochemical measurements were used to investigate if the addition of W to Si improves cycling performance and suppresses Li15Si4 formation. The voltage and differential capacity curves of the Si100-xWx alloys were typical of Si-based alloys, and Si was determined to be the only active phase. Measured capacities agreed with those predicted from quantitative X-ray analysis. The Si-W alloys were found to have high thermal stability, which enables high-temperature processing while maintaining a nanostructured morphology.