Representative By‐Products of Aqueous Zinc‐Vanadium Batteries: Origins, Roles, Strategies, and Prospects

Abstract Aqueous zinc‐ion batteries (AZIBs) are of interest in next‐generation energy storage applications owing to their safety, environmental friendliness, and cost‐effectiveness. Vanadium‐based oxides are promising cathodes for AZIBs due to their appropriate structure and multielectron redox processes. Although hundreds of studies are devoted to understanding the mechanisms and developing high‐performance vanadium‐based cathodes, many puzzles and controversies still exist, especially regarding the two representative by‐products, basic zinc salt (BZS) and zinc pyrovanadate (ZVO). BZS and ZVO are often observed on vanadium‐based cathode and zinc anode during cycling, directly affecting battery performance. However, the two by‐products’ controversial and unclassified insights and unclear mechanisms have severely limited the Zn‐V batteries’ progress. Therefore, this review aims to exhaustively elucidate the “past and present” of the two by‐products following a logical sequence of origin, role, inhibition strategy, and prospect. Notably, the review incorporates substantial comments and understandings of the long‐neglected controversial issues related to the by‐products, especially the BZS‐related energy storage mechanisms and ZVO‐related dissolution mechanisms. This review is expected to provide scientific guidelines for future optimization and commercialization of Zn‐V batteries.