Overcoming Interfacial Hurdles in Solid‐State Aluminum Batteries for Safe and Energy‐Dense Storage

Solid-state aluminum batteries (SSABs), leveraging the high theoretical capacity, natural abundance, and intrinsic safety of the metallic aluminum anode, are regarded as a highly promising energy storage system for the post-lithium era. However, the severe solid-solid interface issues between solid-state electrolytes and electrodes, including high interfacial impedance, sluggish ion transport kinetics, and uncontrollable aluminum dendrite growth, significantly constrain their practical energy density and cycling stability, representing a critical bottleneck toward commercialization. This review aims to systematically elucidate the physicochemical origins of the multi-scale interfacial challenges in SSABs, with a focused discussion on the latest breakthrough strategies in interface design and engineering. It provides an in-depth analysis of how constructing artificial interphases, designing gradient composite electrolytes, tailoring interfacial ion transport pathways, and introducing advanced characterization techniques can effectively promote uniform aluminum plating/stripping, suppress side reactions, and achieve stable interfacial contact. Furthermore, this work prospectively discusses feasible pathways toward compatible high ionic conductivity, excellent mechanical strength, and robust electrochemical stability through integrated interface architectures and synergistic electrode/electrolyte design. Finally, we distill the key challenges and future opportunities spanning from fundamental understanding to device integration, aiming to provide a clear roadmap for developing next-generation SSABs that combine high-energy density with long-term operational safety.