High areal capacitance nickel-cobalt transition metal hydroxide/reduced graphene for structural supercapacitors

Structural supercapacitors (SSCs) as a kind of multifunctional energy storage device, show great potential in zero building energy consumption. Herein, SSCs with cement-based material as electrolytes and layered double hydroxides (LDH) as electrodes were prepared. The electrochemical performance of redox electrodes prepared by different methods was studied. The results show that T-3-rGO/NiCo-LDH prepared by the two-step hydrothermal method exhibits the best performance. Then different asymmetric SSCs with T-3-rGO/NiCo-LDH as positive electrode and rGO as negative electrode were fabricated successfully. Just as we expected, the thinner the thickness of the structural electrolyte is, the higher the areal capacitance. Therefore, the SSCs-1 cm2-0.2 cm prototype device exhibits the best performance, with a high areal capacitance of 255.94 mF/cm2, a high energy density of 79.98 μWh/cm2 at 2 mA/cm2 together with power density of 1500 μW/cm2. On this basis, the SSCs-20.25 cm2-0.2 cm was prepared, which exhibits a high energy density (40.32 μWh/cm2 at 5 mA/cm2) at a power density of 3750 μW/cm2. More importantly, the large-size electrode can carry more active substances, thus storing more electrical energy. Hence, the SSCs show great practical application potential in reducing carbon emissions in the field of large-volume buildings.