A low-cost electrode based on Mg-Co double hydroxide for high energy density structural supercapacitors in civil engineering

In the field of construction, structural supercapacitors (SSCs) have been widely noticed due to their simultaneous functions of load-bearing and energy storage. Unfortunately, the currently available electrodes for SSCs are still aimed at application scenarios such as electronics and electric vehicles, and while their performance is good, they are not applicable to the construction sector, which is massive in scale and extremely cost-sensitive industry. Herein, after trade-off between cost and electrochemical performance, a novel low-cost 3D nanomaterial was designed through a facile approach aimed at increasing the areal energy density of SSCs. By growing Mg-Co double hydroxide nanomaterials directly on nickel foam, we achieved a large areal capacitance of 2577 mF/cm 2 at 5 mA/cm 2 (1136.7 F/g at 2.2 A/g). It also exhibits good cycling stability with a capacitance retention of 82.4 % after 10,000 cycles. In addition, SSCs using magnesium-cobalt double hydroxides achieves a high energy density of 285.6 μWh/cm 3 at a power density of 6.31 mW/cm 3 , which is superior to previously reported structural devices. This demonstrates that Mg-Co double hydroxide electrode has good suitability with SSCs and effectively improves the areal energy density of SSCs. Our proposed method also provides a faster and more reliable pathway for low-cost electrode preparation in SSCs, which may lead to the development of a new generation of SSCs.