Microstructural Tuning of Silicon-Based Anodes and Their Stress Evolution during Electrochemical Cycling

Abstract

Composite electrodes that incorporate oxidized silicon are a cost-effective way to accommodate stresses and extend cycle life. To obtain fundamental information about chemo-mechanical phenomena in these composite structures, several different types of materials are being investigated through tuning the microstructures of Si nanoparticles and composite SiOx particles. The evolution of internal stresses in all of these structures was monitored with precise in situ curvature in conjunction with parallel electrochemical measurements. Ex situ characterization with electron microscopy, x-ray diffraction, and XPS provide important complementary information about changes in the materials. The different types of materials used for this work make it possible to systematically investigate key length scales, by independently varying the microstructures such as oxide layer thicknesses and particle/nano-cluster sizes. Analysis of these results requires assessments and models of both the chemical and mechanical effects of oxide surface layers and silicon encapsulation. The implications for optimizing these composite electrode structures will also be presented.