Layer-by-layer synthesis of Zn-doped MnO$_2$ nanocrystals as cathode materials for aqueous zinc-ion battery

This work first described the new oxidation-reduction route for the synthesis of Zn-doped MnO$_2$nanocrystals via layer-by-layer method as cathode material for an aqueous zinc-ion battery. The obtained nanolayers were characterized by SEM, XRD, XPS and FTIR spectroscopy. The results show the synthesized nanolayers were formed from two-dimensional nanocrystals Zn$_{0.3}$MnO$_2$ the thickness of about 3–8 nm and the morphology of “nanosheets” with the birnessite-like crystal structure. Benefiting from the aqueous 2M ZnSO$_4$ electrolyte and Zn$_{0.3}$MnO$_2$ nanocrystals-based cathode, the zinc-ion battery delivers a high specific capacity (216 mAh/g at 1 A/g) and excellent cycling stability (95% capacity retention after 1000 charge-discharge cycles). The obtained results demonstrate the manganese oxide-based aqueous zinc-ion battery is a promising technology for powering next-generation electronics.