Energy storage properties and mechanical strengths of 3D printed porous concrete structural supercapacitors reinforced by electrodes made of carbon-black-coated Ni foam

To increase the manufacturing efficiency of rechargeable concrete which can alleviate the problem that intermittent new energy is difficult to integrate into the power grid, a new type of concrete structural supercapacitor (CSSC) was proposed here by using mortar-extrusion 3D printing with the carbon-black-coated Ni foam being the electrodes and reinforcement. The printability, energy storage properties, mechanical strengths, and microstructures of the printed CSSC were investigated and analyzed. Results showed adding electrodes increased the buildability because the Ni foam provided more supportiveness for the mortar. However, too many electrodes, especially for thicker ones, would damage the buildability, because thicker electrodes hindered mortar extrusion. The energy storage properties, i.e., the maximum areal capacitance and ionic conductivity of the printed CSSC are 1.59 mF/cm² and 7.2 mS/cm, respectively, which can be increased by using more conductive electrolytes. Furthermore, adding carbon black to the electrodes or increasing the thickness of the electrodes enhanced the areal capacitance and ionic conductivity, because these methods increased the contact area of electrons and ions. The maximum compressive strength and flexural strength of the printed CSSC are 32.5 MPa and 12.9 MPa, respectively, which benefited from better printability and reinforcement. However, more thicker electrodes would over-reinforce the concrete. Moreover, the carbon black reduced the bonding between the printing mortar and Ni foam, resulting in decreased mechanical strength of the printed CSSC. This study provides an efficient method to manufacture the CSSC, and insights into the properties of the printed CSSC, which may facilitate future CSSC applications.