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.