Hybrid nanomaterial of α-Co(OH)2 nanosheets and few-layer graphene as an enhanced electrode material for supercapacitors

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 ot-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 cx-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 ot-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 Fig at 1 A/g, while a better rate capability and better stability were achieved compared to that mad of pristine and single exfoliated c-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 alpha-Co(OH)(2)/few-layer graphene could be a potential electrode material for electrochemical capacitor. (C) 2016 Elsevier Inc. All rights reserved.