Unique MOF-derived hierarchical MnO2 nanotubes@NiCo-LDH/CoS2 nanocage materials as high performance supercapacitors

Abstract

Nanostructure is the most important aspect in the development of high performance supercapacitors. In this work, we designed and developed new one-dimensional hierarchical hollow nickel–cobalt layered double hydroxide nanocages assembled on MnO₂ nanotubes with uniformly dispersed CoS₂ nanoparticles, MnO₂@NiCo-LDH/CoS₂, using a zeolitic imidazolate skeleton (ZIF-67) as the template via multiple hydrothermal and sulfuration processes. This unique one-dimensional hierarchical nanostructure is characterized by a high specific area and high structural stability. The presence of CoS₂ nanoparticles in the nanocage increases the electrical conductivity and enhances the stability of the structure. Electrochemical studies show that MnO₂@NiCo-LDH/CoS₂ electrode materials have a high specific capacitance of 1547 F g⁻¹ at a current density of 1 A g⁻¹ and 1189 F g⁻¹ at 10 A g⁻¹, exhibiting high rate performance (76.9%) and high stability (82.3%), which is substantially better than the performance of most recently reported similar systems. The asymmetric supercapacitor assembled with MnO₂@NiCo-LDH/CoS₂ and activated carbon has a maximum energy density of 50 W h kg⁻¹ and a maximum power density of 9658 W kg⁻¹. The unique nanostructure and excellent performance of the asymmetric supercapacitor in the present study demonstrate a new platform for developing highly efficient supercapacitor materials with high energy density and high power density.