Electrochemical performance of Co-Al layered double hydroxide nanosheets mixed with multiwall carbon nanotubes

Regular hexagonal Co-Al layered double hydroxides (Co-Al LDH) were synthesized by urea-induced homogeneous precipitation. This material proved to be nanosheets by scanning electron microscopy and X-ray diffraction measurements. The electrochemical capacitive behavior of the nanosheets in 1 M KOH solution were evaluated by constant current charge/discharge and cyclic voltammetric measurements, showing a large specific capacitance of 192 F center dot g(-1) even at the high current density of 2 A center dot g(-1). When multiwall carbon nanotubes (MWNTs) were mixed with the Co-Al LDH, it was found that the specific capacitance and long-life performance of all composite electrodes at high current density are superior to pure LDH electrode. When the added MWNTs content is 10 wt%, the specific capacitance increases to 342.4 F center dot g(-1) and remains at a value of 304 F center dot g(-1) until the 400th cycle at 2 A center dot g(-1), showing that this is a promising electrode material for supercapacitors working at heavy load. According to the electrochemical impedance spectra, MWNTs greatly increase the electronic conductivity between MWNTs and the surface of Co-Al LDH, which consequently facilitates the access of ions in the electrolyte and electrons to the electrode/electrolyte interface.