Facile Zn2+ Desolvation Enabled by Local Coordination Engineering for Long-Cycling Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have aroused continuously increasing attention for grid-scale energy storage applications. However, the progress of AZIBs is largely plagued by their sluggish reaction kinetics and poor structural reversibility, which are closely related to the desolvation process of hydrated Zn2+. Herein, a strategy of local coordination engineering is proposed to modulate both surface and bulk structure of a conventional alpha-MnO2 cathode to overcome these issues. Theoretical simulations and experimental characterizations reveal that the surface F coordinations effectively adjust the absorption strength toward H2O and Zn, which facilitates the desolvation of hydrated Zn2+ and thus improves the interfacial ion diffusion rate and reaction kinetics. Meanwhile, the structural integrity is largely enhanced with suppressed irreversible phase evolution over cycling benefiting from the presence of robust Mn-F bonds in the bulk lattice. As a consequence, the achieved cathode exhibits almost no capacity degradation after 400 cycles at a low current density of 0.5 A g(-1) and long-term durability over 3500 cycles at a high current density of 5 A g(-1). The proposed modulation strategy provides new opportunities for designing long-cycling and high-energy cathodes for AZIBs and beyond.

Automated summary

In this study, a strategy of local coordination engineering is proposed to modulate the surface and bulk structure of a conventional alpha-MnO2 cathode for aqueous zinc-ion batteries (AZIBs). This strategy effectively improves the desolvation process of hydrated Zn2+, enhances interfacial ion diffusion rate and reaction kinetics, and suppresses irreversible phase evolution. As a result, the achieved cathode exhibits excellent cycling stability and long-term durability, making it a promising candidate for grid-scale energy storage applications.