Rationally controlled synthesis of Ni-Cu-Zn oxides hollow structures for high performance supercapacitors

Abstract

Designing electrodes with rational components and structures may remarkably boost their electrochemical properties. Hybrid metal oxides electrode with hollow structures show attractive advantages for electrochemical energy storage. Herein, we present a simple synthetic route for preparation of Ni-Cu-Zn oxides yolk-shell sphere (YSS) and hollow sphere (HS) structures as supercapacitors electrodes. A solvothermal method is first conducted to obtain the precursors with YSS and HS structures via regulating the reaction time. The resultant precursors are then converted to Ni-Cu-Zn oxides YSS and HS followed by air calcination. Compositional and structural features render the both Ni-Cu-Zn oxides desirable for supercapacitors application. Particularly, Ni-Cu-Zn oxides HS structures deliver a large capacity of 1114.2 C g-1 at 2.0 A g-1 and a capacitance of 774.4 C g-1 at 20 A g-1 while maintaining 92.5% capacity retention after 10000 cycles. Furthermore, an asymmetrical supercapacitor is constructed using Ni-Cu-Zn oxides HS and actived carbon (AC), showing an energy density of 58.9 W h kg-1 at power density of 1500 W kg-1 and excellent cycling stability. In general, this work not only offers a promising candidate material for supercapacitors electrode, but also provides a simple avenue to prepare hollow structured hybrid metal oxides .