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

BZS (basic zinc salt, Zn_x(An)_y(OH)_z∙nH₂O, An denotes anions) and ZVO (zinc pyrovanadate, Zn₃(OH)₂V₂O₇·2H₂O) are the two representative by-products frequently formed on the cathode or even the anode surface of aqueous zinc-vanadium batteries during cycling. This review aims to exhaustively elucidate the “past and present” of long-neglected by-products in a logical sequence of origins, roles, inhibition strategies, and prospects, driving the efficient design and future commercialization of aqueous Zn-V batteries.

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.