Aqueous Zn-based rechargeable batteries: Recent progress and future perspectives

Benefiting from the advantageous features of high safety, abundant reserves, low cost, and high energy density, aqueous Zn-based rechargeable batteries (AZBs) have received extensive attention as promising candidates for energy storage. To achieve high-performance AZBs with high reversibility and energy density, great efforts have been devoted to overcoming their drawbacks by focusing on the modification of electrode materials and electrolytes. Based on different cathode materials and aqueous electrolytes, the development of aqueous AZBs with different redox mechanisms are discussed in this review, including insertion/extraction chemistries (e.g., Zn2+, alkali metal ion, H+, NH4+, and so forth) dissolution/deposition reactions (e.g., MnO2/Mn2+), redox couples in flow batteries (e.g., I-3(-)/3I(-), Br-2/Br-, and so forth), oxygen electrochemistry (e.g., O-2/OH-, O-2/O-2(2-)), and carbon dioxide electrochemistry (e.g., CO2/CO, CO2/HCOOH). In particular, the basic reaction mechanisms, issues with the Zn electrode, aqueous electrolytes, and cathode materials as well as their design strategies are systematically reviewed. Finally, the remaining challenges faced by AZBs are summarized, and perspectives for further investigations are proposed.