The Impact of Non-uniform Metal Scaffolds on the Performance of 3D Structured Silicon Anodes

Silicon-based anodes are considered to be one of the most competitive candidates for next generation high power/energy density lithium ion batteries. A main drawback limiting their practical application is significant volume changes in Si during lithiation-delithiation, which induce high stresses and cause degradation and pulverization of the anode. A novel structured silicon anode, consisting of a metal scaffold coated with a layer of Si, has been introduced to address this issue and to improve the cycle life performance of Si anodes. In this paper, the impact of non-uniform metal scaffold structures on the mechanical performances of the Si anode is investigated. A multi-physics based finite element (FE) model is developed, where the geometric of the non-uniform structured anode is built based on experimental measurements. The stress distribution and deformation of the anode after full lithiation are predicted and compared with experimental results. It is found that large tensile stress concentrations are shown on the surfaces of Si layers; the volume-expansion induced stress is sensitive to the degree of non-uniformity of the scaffold. Sharp edges on the scaffold could result in high compressive stress. Rounding these edges is found to be a promising approach to reduce stress concentrations and improve the structural integrity of the anode.