Intimately coupled Mn3O4 nanocrystalline@3D honeycomb hierarchical porous network scaffold carbon for high-performance cathode of aqueous zinc-ion batteries

Herein, 3D honeycomb hierarchical porous network scaffold carbon is synthesized by a unique PVP-SiO2-boiling method with the boiling bubbles as soft template and SiO2 nanospheres as hard template. Then MnO2 nanosheets intimately grow on the carbon matrix and are further decomposed to Mn3O4 nanocrystalline with size of 7–9 nm. The obtained Mn3O4 nanocrystalline@3D honeycomb hierarchical porous network scaffold carbon has abundant mesopores and large specific surface area (92 m2 g−1). When used as a cathode material for zinc-ion batteries, the synthesized composites exhibit high reversible capacity (546.2 mAh g−1 at 0.5 A g−1), remarkable cycling stability (discharge capacity of 97.8 mAh g−1 at 3 A g−1 after 600 cycles) and superior rate capability (15.7 mAh g−1 at 10 A g−1). The kinetics analyses indicate zinc storage mechanism includes diffusion process and capacitive process of Zn2+ and H+ ions, and the capacitive storage is dominant. The outstanding zinc storage performance benefits from the structural advantages. The unique carbon matrix improves electronic conductivity of Mn3O4, facilitates penetration of electrolyte, and well supports Mn3O4 nanocrystalline. The small size and large specific surface area of Mn3O4 nanocrystalline induce significant capacitive storage effect.