Zn3V3O8@ZnO@NC heterostructure for stable zinc ion storage from assembling nanodisks into cross-stacked architecture

In the last decades, aqueous zinc-ions batteries (AZIBs) have attained enormous attention owing to their envi-ronmental friendliness, the abundant resources of Zn and the safety of aqueous electrolytes. However, the sluggish zinc-ions diffusion rate results in poor electrochemical properties. Therefore, seeking an appropriate cathode material is a brilliant method to deal with this problem. In this work, the heterostructure of Zn3V3O8 and ZnO encapsulating into 3D interpenetrating carbon network (Zn3V3O8@ZnO@NC) is prepared to serve as cathode material for AZIBs. Benefiting from the structural stability of the cross-stacked structure and outstanding electrochemical conductivity of the 3D interpenetrating carbon network, the electrode material delivers remarkable cyclic stability (120.5 mA h g-1 at 5 A g-1 after 2000 cycles). The discharge capacity only reduces 33.3 mAh g-1 with the current density increase from 0.5 A g-1 to 3 A g-1 (216.3 mA h g-1 and 183 mA h g-1 at 0.5 A g-1 and 3 A g-1, respectively), revealing a super-stable rate performance. Besides, the zinc ion storage mechanism of Zn3V3O8@ZnO@NC was revealed via ex-situ XRD and XPS characterizations. The results reveal that Zn3V3O8@ZnO@NC was transformed into Zn3(OH)2V2O7???2H2O (ZOVO) during the first charge process between 1.2 and 1.4 V and the transformation is completed after the two cycles. After the second cycle, the Zn2+ storage is provided only by the de(intercalation) of Zn2+ in ZOVO.