Advances in aqueous zinc-ion battery systems: Cathode materials and chemistry

Renewable energy has been extensively developed to curb the greenhouse effect and reduce carbon dioxide emissions. Nevertheless, their applications are greatly limited due to the intermittence and instability nature. Therefore, reasonably store and distribution of new energy have become a widespread concern. Among various energy storage technologies, lithium-ion battery technology has achieved great success, but the scarcity of lithium resources and the use of toxic and flammable organic electrolytes have limited its further development. Oppositely, aqueous zinc ion batteries (AZIBs) have advantages of safety, abundant resources, low cost, and the potential to store energy at the power plant level. However, the low capacity, poor cycle stability, and low voltage of cathode materials have become one of the limiting factors for the application of AZIBs. Herein, we systematically summarize and discuss the reported cathode materials, including manganese-based oxides, vanadium-based compounds, Prussian blue analogues, organics, MXenes, transition metal chalcogenides, layered double hydroxides, and others. Their developments, challenges, and feasible modification strategies are thoroughly analyzed. In addition, we also summarize and compare the proposed energy storage mechanisms of cathode materials. Finally, we propose potential research directions in the future for cathode materials, and provide essential guidance for the development of high-performance AZIBs.