Supercapacitor with metal hydroxide nanosheets as electrode can have high capacitance. However, the cycling stability and high rate capacity is low due to the low electrical conductivity. Here, the exfoliated α-Co(OH)2 nanosheets with high capacitance has been assembled on few-layer graphene with high electric conductivity by a facile yet effective and scalable solution method. Exfoliated hydrotalcite-like α-Co(OH)2 nanosheets and few-layer graphene suspensions were prepared by a simple ultrasonication in formamide and N-methyl-2-pyrrolidone, respectively. Subsequently, a hybrid was made by self-assembly of α-Co(OH)2 and few-layer graphene when the two dispersions were mixed at room temperature. The hybrid material provided a high specific capacitance of 567.1 F/g at 1 A/g, while a better rate capability and better stability were achieved compared to that mad of pristine and single exfoliated α-Co(OH)2. When the hybrid nanocomposite was used as a positive electrode and activated carbon was applied as negative electrode to assembly an asymmetric capacitor, an energy density of 21.2 Wh/kg at a power density of 0.41 kW/kg within a potential of 1.65 V was delivered. The high electrochemical performance and facile solution-based synthesis method suggested that the hybrid of exfoliated α-Co(OH)2/few-layer graphene could be a potential electrode material for electrochemical capacitor.
- Cobalt hydroxide
- Electrochemical capacitor
- Few-layer graphene
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films
- Colloid and Surface Chemistry