To meet growing energy demands, degradation mechanisms of energy storage devices must be better understood. As a non-destructive tool, X-ray Computed Tomography (CT) has been increasingly used by the battery community to perform $textit{in-situ}$ experiments that can investigate dynamic phenomena. However, few have used X-ray CT to study representative battery systems over long cycle lifetimes (>100 cycles). Here, we report the $textit{in-situ}$ CT study of Zn-Ag batteries and demonstrate the effects of current collector parasitic gassing over long-term storage and cycling. We design performance representative $textit{in-situ}$ CT cells that can achieve >250 cycles at a high areal capacity of $mathrm{12.5;mAh/cm^2}$. Combined with electrochemical experiments, the effects of current collector parasitic gassing are revealed with micro-scale CT (MicroCT). The volume expansion and evolution of ZnO and Zn depletion is quantified with cycling and elevated temperature testing. The experimental insights are then utilized to develop larger form-factor $mathrm{4;cm^2}$ cells with electrochemically compatible current collectors. With this, we demonstrate over 325 cycles at a high capacity of $mathrm{12.5;mAh/cm^2}$ for a $mathrm{4;cm^2}$ form-factor. This work demonstrates that $textit{in-situ}$ X-ray CT used in long cycle-lifetime studies can be applied to examine a multitude of other battery chemistries to improve their performances.
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