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 (VO_x) 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 VO_x 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 VO_x cathode. Theoretical calculations and synchrotron radiation have verified that the high-valence Al³⁺ plays dual roles of competing with Zn²⁺ for solvation and forming a Zn−Al alloy layer with a homogeneous electric field on the anode surface to mitigate the side reactions and dendrite generation. The Al-containing cathode–electrolyte interface (CEI) considerably alleviates the irreversible dissolution of the VO_x 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 VO_x cathodes (VO₂, V₂O₅ and NH₄V₄O₁₀) in the ZS−KASO electrolyte showed excellent cycling stability, including Zn powder||VO₂ cells and Zn||VO₂ pouch cells. Even better, the full cell exhibits excellent cycling stability at low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm⁻²). This study offers a straightforward and practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.