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

Abstract 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 ZnSO 4 (ZS) electrolyte, KAl(SO 4 ) 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 Al 3+ plays dual roles of competing with Zn 2+ 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 (VO 2 , V 2 O 5 and NH 4 V 4 O 10 ) in the ZS−KASO electrolyte showed excellent cycling stability, including Zn powder||VO 2 cells and Zn||VO 2 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.