In this study, we report in situ measurements of lithium diffusion induced stress in patterned amorphous Si negative electrodes. This configuration was used as a model system to understand how the gap between islands can accommodate the large volume expansion and stress generation that occurs during the lithiation of Si. The effect of pattern size was studied systematically with 7 μm, 17 μm and 40 μm square islands. Experimentally measured stresses were then compared to a continuum model that describes stress accommodation due to interfacial sliding or plastic deformation in the underlying current collector. These results indicate that engineering an appropriately sized Si island is an effective method for mitigating lithiation-induced stress and mechanical degradation in Si based electrodes.