High Performance Aluminum Ion Batteries Enabled by the Coordination Between Vanadium‐Based PBAs Cathode and Aqueous Eutectic Electrolyte

Abstract The practical application of aqueous aluminumion batteries (AAlBs) faced with critical challenges, such as low rate performance and poor cycling stability due to the absence of ideal cathode materials. To address the bottlenecks of low electrochemical activity, structural instability, and narrow voltage window in Prussian blue analogues (PBAs) for AAIBs, this study develops a universal synthesis strategy integrating acid‐assisted method with ligand modulation to prepare high‐performance vanadium‐based PBAs (V‐PBAs) cathodes. Through precise coordination environment control, V and Fe/Co/Ni synergistically enhance multi‐electron redox activity. Density functional theory calculations reveal that the Fe‐doped VFePBA exhibits a narrow bandgap (0.479 eV) and low Al 3+ migration energy barrier (0.586 eV), enabling rapid ion transport. Combined with an Al 2 (SO 4 ) 3 ‐urea eutectic electrolyte (AU15) that expands the operational voltage window to 0.1–2.0 V, the optimized Zn||AU15||VFePBA system achieves a high specific capacity of 161.37 mAh g −1 at 0.1 A g −1 . In‐situ characterizations confirm a suppressed structural distortion via Al‐O coordination and a capacitive‐dominated charge storage mechanism. Flexible pouch cells demonstrate stable operation under mechanical bending and practical device powering capabilities. This work provides a novel paradigm for the systematic assembly of advanced safe, and low‐cost post‐lithium energy storage systems.