Quantifying the 2D anisotropic displacement and strain fields in graphite-based electrode via in situ scanning electron microscopy and digital image correlation

During charge and discharge of the lithium-ion batteries, deformation in the graphite-based electrode can induce high local strains and severe mechanical degradation. However, little quantitative method are available to help understand the mechanisms of deformation evolution at the microscopic scales. This work reports a combined method via in-situ scanning electron microscopy and digital image correlation technology to characterize the two-dimensional displacement and strain fields of the electrode throughout operation. It is found that 50% irreversible swelling in the initial cycle and reversible anisotropic deformation in the following cycles. The average strain in the vertical direction is 4.94%, which is about 18 times higher than that in the horizontal direction of electrode. This new combined method based on in-situ scanning electron microscopy and digital image correlation can be used to quantify the evolution of the displacement and stain fields in the electrode.