Na-ion batteries are gaining attention as alternative to Li-ion batteries. Large volume changes and associated stresses in high performance electrodes (e.g. Si, Sn, Ge) of Li-ion and Na-ion batteries is a significant challenge that need to be address in order for these new technologies to be commercially viable. To this end, we performed real-time measurements of stresses generated in Li-ion and Na-ion electrodes during electrochemical cycling. Based on the experimental observations, a continuum mechanics model was developed that accounts for large deformation, diffusion, and electrochemical phenomenon necessary to design future batteries and address the current challenges. To validate the robustness of this theory we have applied it to both Na and Li electrode systems. Our theory captures the stress and electrochemical response in both Li-Ge and Na-Ge electrode systems. In this talk we will present our theory along with the experimental results.