Strategies for electrolyte modification in aqueous zinc-ion batteries: an antisolvent approach

The advancement of zinc-ion batteries (ZIBs) has been impeded by issues associated with the aqueous electrolyte, including hydrogen evolution, dendritic growth, and limited electrochemical stability. Additionally, the decomposition of the aqueous electrolytes presents a significant challenge. A viable strategy to address these impediments involves the modification of aqueous electrolytes through the incorporation of antisolvents, which can enhance the charge storage capability and energy density of ZIBs. The concept of antisolvent plays a crucial role in modulating the inner and outer ionic spheres and enhances the electrolyte's ability to suppress side reactions and mitigate zinc dendrite formation by modulating solvation structures and ionic interactions. This improves the ion insertion/deinsertion mechanism and, subsequently, the cycle stability. This modification also expands the electrolyte's electrochemical stability window, enabling higher operating voltages and better compatibility with advanced cathode materials. This feature review article summarises the recent advancements in electrolyte modification in aqueous Zn-ion batteries (AZIBs). Mainly, the advantages, significant challenges, and mechanism of electrolyte alteration for AZIBs have been discussed. The explicit selection criteria for antisolvents, considering their properties and modulations in the solvation structure and their impact on the performance as a function of operating conditions, are explained. Lastly, the mechanism of the effect of antisolvent on the aqueous electrolyte, considering the regulation of solvation sheath and electrode/electrolyte interface, is described. In addition, our contributions to the field of electrolyte modification for AZIBs with an antisolvent approach to tuning the electrolyte structure, transport number, diffusion coefficient, water numbers and their interaction in the solvation shells are also discussed. These insights pave the way for the realization towards the high performance of AZIBs through electrolyte engineering.