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.