Symmetric self-hybrid supercapacitor consisting of multiwall carbon nanotubes and co-al layered double hydroxides

Multiwall carbon nanotubes (MWCNTs) and Co-Al layered double hydroxides (Co-Al LDH), as two electroactive materials, were integrated in one electrode to form a self-hybrid composite electrode on the basis that different materials should match correctly according to their respective charge-storage mechanisms. Our emphasis is not put on elevating electric conductivity and reducing the added amount of noble metal oxide in the composite but on prolonging work potential range through proper balance of two active materials. A symmetric supercapacitor made up of two pieces of the self-hybrid composite electrodes was assembled. Cyclic voltammetry (CV) and chronopotentiometric techniques were employed to evaluate the electrochemical behaviors of the self-hybrid supercapacitor in 1 M KOH solution. The results show that the CV curves approach rectangle shapes and that charge and discharge curves are basically symmetrical. Compared to MWCNTs/MWCNTs symmetric supercapacitor, this new supercapacitor has good long-term stability, larger maximum power and energy density (6400 W kg(-1), 13.2 Wh kg(-1)), and a higher specific capacitance of 15.2 F g(-1) even after 1000 cycles at a large current of 2 A g(-1). (c) 2007 The Electrochemical Society.