Hydrothermal synthesis of 3D NixCo1-xS2 particles/graphene composite hydrogels for high performance supercapacitors

In this work, three dimensional (3D) NixCo1-xS2/graphene composite hydrogels with different Ni contents (denoted as NixCo1-xS2/GH (x = 0, 0.31, 0.56, 0.66, 1)) have been synthesized by a simple one-step hydrothermal method and utilized as the active materials of supercapacitors. The as-prepared samples present a 3D interconnected porous network with the pore sizes in the range of several to tens micrometers. Interestingly, the NixCo1-xS2 particles are uniformly located on the graphene network and the particle size is evolved from similar to 50 nm to similar to 1.5 mu m with the increase of Ni content. The electrochemical measurements revealed that the specific capacitance, rate capability and cyclability of different NixCo1-xS2/GH electrodes are strongly affected by their different Ni content. Among these, the 3D Ni0.31Co0.69S2/GH composite has the highest specific capacitance of 1166 F/g at a current density of 1 A/g. Furthermore, a specific capacitance of 559 F/g can be still maintained at high current density of 20 A/g. After 1000 charge-discharge cycles at 5 A/g, the specific capacitance remains a high value of 755 F/g. (C) 2015 Elsevier Ltd. All rights reserved.