Cycling effect on morphological and interfacial properties of RuO 2 anode film in thin-film lithium ion microbatteries

Abstract

This work presents a comprehensive study on the effects of lithiation/delithiation process (discharge/charge cycling) on the structure, morphologies, and nanomechanical and interfacial properties of sputtered RuO2 film, which is used as anode in thin-film lithium ion batteries. Various techniques including ex situ X-ray diffraction (XRD), atomic force microscope (AFM), nanoindentation tests combining with focused ion beaming (FIB) sectioning, and scanning electron microscope (SEM), are used in this study. The results reveal significant changes in the surface morphology and roughness of the anode film because of the large volume changes induced by the phase transformation involving Li+. It also shows that the electrode film mechanically fails because of the repeated volume changes and this process is related to the generation/relaxation of stress during the discharge/charge cycling. The induced stress in the film intensifies the initiation and propagation of microcracks, as well as the interfacial delamination. The morphological and nanomechanical property changes have harmful effects on the electrical contact between the film and the substrate, resulting in the degradation of battery. © 2011 The Minerals, Metals & Materials Society and ASM International.