Recent Advances in Electrolytes for "Beyond Aqueous" Zinc-Ion Batteries

With the growing demands for large-scale energy storage, Zn-ion batteries (ZIBs) with distinct advantages, including resource abundance, low-cost, high-safety, and acceptable energy density, are considered as potential substitutes for Li-ion batteries. Although numerous efforts are devoted to design and develop high performance cathodes and aqueous electrolytes for ZIBs, many challenges, such as hydrogen evolution reaction, water evaporation, and liquid leakage, have greatly hindered the development of aqueous ZIBs. Developing "beyond aqueous" electrolytes can be able to avoid these issues due to the absence of water, which are beneficial for the achieving of highly efficient ZIBs. In this review, the recent development of the "beyond aqueous" electrolytes, including conventional organic electrolytes, ionic liquid, all-solid-state, quasi-solid-state electrolytes, and deep eutectic electrolytes are presented. The critical issues and the corresponding strategies of the designing of "beyond aqueous" electrolytes for ZIBs are also summarized.