Guest Editorial for the Special Issue on Aqueous Electrolyte Batteries

The stability and energy density of aqueous energy storage systems have improved considerably over the past decade due to the continuous development of electrode active materials and aqueous electrolytes. Aqueous energy storage is considered to be an alternative to current lithium-ion batteries. It is a favorable choice for the foreseeable future in terms of configurations involving high safety and low cost, especially in large-scale energy storage. Although it is seen to be breaking through close to the boundaries of practical applications, the development still needs to break through some bottlenecks, such as side reactions caused by aqueous environment electrolytes. Additionally, issues such as electrode materials' kinetic and thermodynamic stability when ions are in an aqueous environment require novel chemical design, fabrication, and testing principles. To contribute some ideas on how to address these issues, the special issue presents a focused review of current progress in i) proton-based battery chemistry, ii) aqueous aluminum metal batteries, iii) aqueous lithium-ion batteries, iv) aqueous zinc ion batteries, v) smart aqueous batteries, and vi) energy storage and conversion in electric eels biomimetics. In particular, for the zinc ion batteries being currently intensively investigated, this special issue covers recent progress on their positive electrode, negative electrode, and electrolyte. These excellent works are exemplars of recent trends in aqueous energy storage at the forefront of the field, which aim to improve well-established processes in applications and attract more researchers together to promote the development of aqueous energy storage. We thank all the contributing authors, reviewers, and editorial and production staff for making this themed issue possible. The authors declare no conflict of interest.