Solid oxides are attractive electrolyte materials for all-solid-state lithium batteries (ASSLBs) owing to their high stability and pure Li-ion conductivity. Nevertheless, the electrochemical performance of ASSLBs employing solid oxide-based electrolytes cannot compete with ASSLBs with sulfide or polymeric electrolytes due to poor interfacial contact and high boundary resistance between the active materials and solid oxide electrolytes. To overcome this hurdle, elaborate microstructural analysis of the interface of the active material/solid oxide electrolyte in ASSLBs is essentially required since the interfacial contact area dominantly acts as the ion pathway and the electrochemical reaction site in the electrode. Although recent attempts on interfacial structure analysis of ASSLBs have provided simple 2D or semi-3D microstructural features, the results have not yielded deep insights. Herein, we investigated the interfacial defects in an all-solid-state electrode with a solid oxide electrolyte via a 3D digital twin technology combining 3D structural quantification and physico-electrochemical simulations to unravel the intrinsic limitations of solid oxide electrolytes. The in-depth results can be used to design materials and optimize electrode design parameters for ASSLBs.