Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High‐performance Aqueous Zinc–Vanadium Batteries

A zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn–ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi‐functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in‐situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high‐valence Al3+ plays multifunctional roles of competing with Zn2+ for solvation and forming a Zn–Al alloy layer with a homogeneous electric field to mitigate the side reactions and dendrite generation. The Al‐containing cathode–electrolyte interface considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn || Zn cell with KASO exhibits an ultra‐long cycle of 6000 h at 2 mA cm−2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS–KASO electrolyte showed excellent cycling stability, even at a low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm‐2). This study offers a practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.