Constructing metal-organic framework-derived Mn2O3 multishelled hollow nanospheres for high-performance cathode of aqueous zinc-ion batteries

Herein, we successfully synthesize Mn2O3 multishelled hollow nanospheres through simply oxidizing Mn-based metal-organic framework microspheres. The number of the shells reaches 4. Many cavities and nanograins are hidden underneath the shell. The multishelled hollow structure brings about a wide hierarchical mesopore size range, large pore volume (0.26 cm3 g-1) and high specific surface area (117.6 m2 g-1). The superior zinc-ion storage performance may be achieved. The reversible capacity reaches 453 mAh g-1 at current density of 0.1 A g-1. After 500 cycles at 1 A g-1, the discharge capacity of 152.8 mAh g-1 is still delivered. The discharge capacity at 1.5 A g-1 stabilizes at 107 mAh g-1. The zinc storage process is further studied through kinetics analyses. It is found that in the zinc storage process, ion-diffusion process and capacitive process occur simultaneously, and the capacitive process is dominant. The excellent electrochemical performance is mainly attributed to the multishelled hollow nanosphere structure of Mn2O3. This structure promotes contact of electrode materials/electrolyte, offers more active sites, facilitates infiltration of electrolyte, buffer volume change of Mn2O3, improving electrochemical activity, reaction kinetics and cycling performance of Mn2O3. Overall, Mn2O3 multishelled hollow nanosphere is an excellent cathode material for aqueous zinc-ion batteries.