Crystalline NiCo2O4 and amorphous NiCo2S4 heterostructured electrode for high-performance asymmetric supercapacitors

Abstract

The construction of well-designed heterostructures and phase engineering have been verified to be a promising strategy to improve electrochemical performance of supercapacitors. However, it is still a challenge to construct well-defined amorphous/crystalline hetero-phase electrode with plentiful heterointerfaces. Herein, a high-performance self-supported NiCo2O4@NiCo2S4 electrode with crystalline NiCo2O4 and amorphous NiCo2S4 heterostructure is synthesized by electrodeposition-anneal-electrodeposition procedure. The interconnected nanosheet structure and rich heterointerfaces effectively promote the exposure of surface area and accelerate the electron/ion transfer kinetics of redox reaction as well as restrain the volume expansion and structural collapse, thus greatly enhancing the electrochemical performance and stability. Impressively, the advanced NiCo2O4@NiCo2S4 electrode delivers a prominent specific capacitance of 2243.0 F g−1 at 1 A g−1 along with outstanding cyclic stability with a capacity retention of 83.29 % at 10 A g−1 after 5000 cycles. Moreover, the asymmetric supercapacitor (ASC) assembled by NiCo2O4@NiCo2S4 cathode and active carbon anode displays a maximum energy density of 66.7 Wh kg−1 at 625.3 W kg−1 and favorable cycling stability (77.23 % after 10,000 cycles at 10 A g−1).