Synthesis of CuO@CoNi LDH on Cu foam for high-performance supercapacitors.

• The cross-linked hierarchical CuO@CoNi LDH was facilely synthesized. • The cross-linked CuO@CoNi LDH growing on Cu foams has obviously stronger adhesive force. • The assembled CF@CuO@CoNi LDH 1–4//RGO asymmetric supercapacitor indicates extraordinary energy density. Core-shell nanostructured compounds are considered as promising electrode materials for supercapacitors in virtue of their facile accessibility to active sites and high electrical conductivity, yet always limited by low capacity or poor cyclic stability because of the weak combination or shedding of active materials from the substrate. To address this issue, we first synthesize three-dimensional (3D) CuO cross-linked nanosheet aggregates grown on Cu foams (CF) by wet chemical oxidation, and further demonstrate the growth of ultra-thin cobalt-nickel layered double hydroxides (CoNi LDH) onto the core of 3D CuO cross-linked nanosheet aggregates by electrodeposition. In this way, we find that the cross-linked CuO@CoNi LDH growing on Cu foams has stronger adhesive force. The as-prepared core-shell nanohybrid (CF@CuO@CoNi LDH) is featured with a high specific capacity (319.4 mAh·g−1 at 1 A·g−1), excellent rate performance and long cycling stability. The as-assembled CF@CuO@CoNi LDH 1–4//RGO asymmetric supercapacitor (ASC) delivers an ultra-high energy density of 92.5 Wh·kg−1 at a power density of 400 W·kg−1, as well as an excellent cycling performance with capacitance retention of 83.8% after 8000 cycles at 5 A·g−1. These results indicate that the cross-linked hybrid is a high-performance electrode material for supercapacitors, and could provide new insight into the synthesis of novel core-shell nanomaterials. [ABSTRACT FROM AUTHOR]