Built-in electric field boosted ionic transport kinetics in the heterostructured ZnCoO/ZnO nanobelts for high-performance supercapacitor.

Metal oxides are promising electrode candidates for supercapacitor due to their high theoretical capacitance, good reversibility, and low cost. However, they show inferior specific capacitance and power density because of their sluggish ion diffusion kinetics and intrinsically poor electrical conductivity within the solid phase. Herein, heterostructured ZnCoO/ZnO nanobelts are successfully prepared by using self-assembled Zn/Co-based nanosized coordination polymers as the precursors. The resulted nanobelts are composed of uniformly distributed ZnCoO and ZnO nanocrystals, which spontaneously develop built-in electric fields in the nanobelts, and thus improve the conductivity and accelerate charge transport. The as-obtained ZnCoO/ZnO nanobelts display a high specific capacitance of 481.0 F g at 1 A/g. The asymmetric supercapacitor, with a ZnCoO/ZnO positive electrode and an activated carbon negative electrode, deliver an energy of 23.77 Wh kg at the power density of 399.98 W kg and excellent prolonged cycle life. The excellent electrochemical performance benefits from both the special structure and built-in field at the heterostructure interface, which could significantly reduce the ion diffusion resistance and thus promote charge transport. This strategy may blaze a trail for engineering efficient electrode based on earth-abundant materials.