Due to the high theoretical capacity and environmental benignity, the tin
(Sn) anode is one of the most promising candidates for applications as an
electrode. Using an image-based finite element approach, we rebuilt the Sn active
phase and evaluated the distribution of Li-ion concentration and evolution of
stress. To account for the large deformation of the Sn electrode during the
charge/discharge process, we proposed a theoretical framework based on
viscoplasticity theory to study the chemomechanical coupling behavior of the Sn
anode. First, we applied finite deformation theory to investigate the proposal that
viscoplasticity induced the reduction in von Mises stress. Then, considering the
stress-dependent diffusion in Li-Sn systems, the effects of microstructure on the stress
evolution, local electric potential, and cycle performance were elucidated. Our
results revealed that the microstructure significantly influenced the stress field
and distribution of electric potential. Additionally, our results showed that
concentration distributions result in a sharp gradient and that the von Mises stress
varied significantly at the chosen concave or convex sites of the surface.
Then, we proposed the effects of the number of cycles on the plastic stress
and the stress-biased voltage. As a result, the predicted behavior of real
microstructure has the potential to be utilized in the design of electrodes with
tunable microstructure.
Keywords
viscoplasticity, lithium concentration, stress evolution,
electric potential, cycle performance