Physical Vapor Deposition Cluster Arrival Energy Enhances the Electrochemical Performance of Silicon Thin-Film Anodes for Li-Ion Batteries

Abstract

Silicon is a leading candidate material to replace carbon/graphite, the commonly used anode material in lithium-ion batteries (LIBs), because it has an 11 times higher theoretical specific capacity. However, silicon anodes have two main issues, low electronic conductivity and large volume expansion during cycling, and these issues present challenges in the manufacture of mechanically stable high-electrochemical-performance Si electrodes. Physical vapor deposition (PVD) is an alternative fabrication process that can produce binderless compact Si thin films suitable for microbatteries and thin flexible devices. Despite numerous studies exploring the use of vacuum-based PVD silicon films, no definitive information has been recorded correlating how changes in process parameters affect the properties of the resulting deposited films and how this influences anode performance in Li-ion batteries. In this work, process parameters (i.e., deposition power and gas working pressure) were altered for various Si film deposition trials. Electronic resistivity, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), residual film stress, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurements were performed for a thorough physico/chemico analysis of the various films. This information was used to interpret the differences in discharge capacity and capacity retention obtained from the various Si anodes using galvanostatic charge/discharge cycling from assembled coin cells. CV measurements were used to corroborate performance outcomes, as well as to calculate Li-ion diffusion coefficients.