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

Herein, we successfully synthesize MnOmultishelled 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 cmg) and high specific surface area (117.6 mg). The superior zinc-ion storage performance may be achieved. The reversible capacity reaches 453 mAh gat current density of 0.1 A g. After 500 cycles at 1 A g, the discharge capacity of 152.8 mAh gis still delivered. The discharge capacity at 1.5 A gstabilizes at 107 mAh g. 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 MnO. This structure promotes contact of electrode materials/electrolyte, offers more active sites, facilitates infiltration of electrolyte, buffer volume change of MnO, improving electrochemical activity, reaction kinetics and cycling performance of MnO. Overall, MnOmultishelled hollow nanosphere is an excellent cathode material for aqueous zinc-ion batteries.