Synthesis and properties of flexible supercapacitor based on Zinc-Aluminum layered doubled hydroxide

Abstract

A flexible, effective supercapacitor using zinc-aluminum-layered double hydroxides (Zn-Al LDHs) as an electrode material is reported. Nanosheets of Zn-Al LDHs were synthesized using a chemical bath deposition method, and they were present in a well-standing shape covering the complete area of the Al foil. The imaging of these nanosheets showed that their average thickness is between 60 and 80nm, with a width and length average of 1.3 and 0.6 μm, respectively. These dimensions help to create the connection arrangements of sheets with a high specific surface area of 88 m2/g which increased electrochemical active sites for charge storage. The X-ray diffraction further approves the structural properties of the prepared material. The flexibility of the supercapacitor was examined by bending and folding up the device to 180° with little mechanical deformation. The highest capacitance value is found to be ~597F/g in the case of the flat condition. The capacitance value decreased to ~387F/g after folding the device 30°, and these values drooped slightly after more increasing the folding angle. The energy density (ED) remains nearly constant at any folding angle (ED=3.39Wh/kg at 30° and ED=3.7Wh/kg at 135°), and similarly, the power density (PD) remains nearly constant (PD=27kW/kg at 30° and 135°). The aforementioned approves the flexibility of the Zn-Al LHD because it provides lifelong stability (87% retaining after 2000 charge/discharge cycles) and stable efficiency after different bending and twisting conditions. The impedance measurements along with the obtained equivalent circuits confirm the electrical characteristics of the as-prepared electrodes with low equivalent series resistances, ensuing the promising conductive path in the supercapacitor device.