In Situ Measurement of Strain Evolution in the Graphene Electrode during Electrochemical Lithiation and Delithiation

The strain/stress of the electrode materials induced in the electrochemical process is the key factor for lithium-ion batteries. However, in situ experimental techniques to quantitatively measure the strain/stress response of electrode materials at different length and time scales are still lacking. In this paper, in situ measurement of strain evolution in the graphene electrode during lithiation/delithiation was performed by micro-Raman spectroscopy. The Raman G and 2D peaks of the graphene electrode were obtained using a modified coin cell with an optical window. The stages of the Li-graphite intercalation compounds were characterized by the G peak, while the in-plane strain of the graphene electrode microstructure was characterized by the 2D peak. Evolution of the biaxial strain during the electrochemical cycles was obtained based on determination of the relationship between the Raman shift and the in-plane strain of the graphene electrode. The experimental results show that the biaxial tensile strain of the graphene electrode almost linearly increases during lithiation. The maximum biaxial tensile strain induced by lithiation is about 0.4%, corresponding to the Li-graphite intercalation compound at stage 3. This study provides an experimental basis for understanding the deformation mechanism of the graphene electrode and developing high-performance graphene-based batteries.