Regulating fast cationic redox for high areal-energy-density structural supercapacitors

Structural supercapacitor (SSC) with cement-based materials as electrolytes shows great potential in the construction field due to their high strength and low cost. However, current SSC usually suffer from low areal capacitance and energy density, especially under a specific mechanical strength, limiting their feasibility of a practical application. Herein, a new type of SSC using cement-polyacrylamide (PAM)-Mn(NO3)2 as a redox electrolyte is proposed to realize high areal capacitance and energy density at high mechanical strength. The results show that introducing PAM and Mn2+ largely improves the ionic conductivity and mechanical properties of the cement-based structural electrolyte, both of which are beneficial to high areal capacitance and energy density. Compared with the pure cement electrolyte, the high ionic conductivity, compressive strength, and flexural strength of the redox structural electrolyte (containing PAM and 4 wt% Mn2+) is increased by 91.52 %, 25.80 %, and 60.79 %, respectively. As a proof-concept-application, the areal energy density (0.038 mWh/cm2, at 1 mA/cm2) of the SSC prepared by the redox structural electrolyte is 9 times higher than that of the pure one (0.004 mWh/cm2). Moreover, there is a slight increase in its electrochemical performance even under a pressure of 200 g.