In Situ Experimental Measurement of the Mechanical Properties of Carbon-Based Electrodes during the Electrochemical Process

Abstract

The mechanics of battery electrodes are crucial for determining the cycling performance and battery lifetime. In this study, we investigated the fundamental important material properties of commercial carbon electrodes that strongly depend on the Li concentration. An optical system is used to perform in situ measurements of a mesocarbon microbead (MCMB) composite electrode during the electrochemical process in a homemade cell with a glass window. The deformation vs. capacity during the second lithiation is given and, combined with a built elastic modulus equation, the elastic modulus of carbon composite electrode is directly quantitatively characterized herein as a function of Li concentration by in situ experiments. It is found that the mechanical responses of the MCMB composite electrode somewhat depend on the graphite intercalation compound stage behavior. The material stiffening of the MCMB composite electrode is experimentally observed herein. Further, the elastic modulus varies nonlinearly with Li concentration. It initially increases, decreases, and then increases again from an initial value of 98 to a maximum of 194 MPa, which is a stiffening factor of two rather than the expected values of three. This experimental data are useful for understanding the relationship between the mechanics and the electrochemistry.