Understanding degradation mechanisms in spray-coated alternating silicon-carbon thin films as anodes for lithium-ion batteries

Abstract

Silicon's high specific capacity makes it one of the most promising new materials for anode applications. However, its performance is limited by its cycling stability. Approaches to remedy the various degradation mechanisms (pulverization, delamination and excessive solid electrolyte interphase (SEI) formation) include the use of silicon-carbon (Si/C) composites or the manufacturing of thin layers. In this study, two approaches were combined by producing alternating silicon and reduced graphene oxide (rGO) layers using a spray-coating process. This allowed us to draw important conclusions regarding the relationship between the silicon layer thickness and the total silicon content of the electrode and the resulting degradation behavior. Moreover, this study examined the suitability of prelithiated polyacrylic acid (LiPAA) as binder for spray-coating and its electrochemical performance. Using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and optical microscopy cross-sections, electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT) and galvanostatic cycling, it could be demonstrated that the silicon layer thickness is a limiting factor for a stable cycling performance and can therefore result in an inhomogeneous charge distribution within the electrode. Understanding the correlation between the layer morphology and degradation behavior is essential to allow for the realization of composite electrodes with a high capacity retention.