Recent progress and challenges of high-loading cathodes for aqueous Zn-ion batteries

Owing to the advantages of low cost, rich resources, and intrinsic safety, aqueous Zn-ion batteries have attracted broad attention as the promising energy storage technology for large-scale smart grids. The cathodes for aqueous Zn-ion batteries have developed rapidly, including Mn-based cathodes, V-based cathodes, and halogen cathodes. High specific capacity and long cycling lifespan have been achieved. However, when the mass loading for cathode materials is scaled up to the practical level, the cycling stability and rate property of aqueous Zn-ion batteries are very unsatisfactory. Therefore, in this review, we deeply analyze the key issues that limit the electrochemical performance of high-loading cathodes for aqueous Zn-ion batteries. Subsequently, we comprehensively summarize the effective solutions to the above issues, including (1) rational binder design, (2) three-dimensional cathode design, (3) cathode material structural optimization, and (4) interface engineering for Zn anodes. Finally, we give a critical perspective from commercial application for the future development of high-loading cathodes for high-energy-density aqueous Zn-ion batteries.