Improved Energy Storage of Dual-Concrete Composite Cavity-Structure Supercapacitor Fabricated via Mortar-Extrusion 3D Printing (2026-04)¶

The integration of energy storage functionality into structural components is a promising strategy for developing self-sufficient buildings powered by intermittent renewable sources. This study presents a dual-concrete composite cavity-structure supercapacitor (DCC-CSSC) fabricated via mortar-extrusion 3D printing, which combines a load-bearing concrete matrix with designed internal cavities filled with an ion-permeable concrete electrolyte. The proposed cavity-filling strategy enhances energy storage performance: The DCC-CSSC achieved areal capacitances of 50.9–59.7 mF/cm2, representing up to a 25-fold increase compared to single-material solid concrete designs. Ionic conductivity reached 2.1–4.6 mS/cm, with a maximum improvement of 283.3% over single-material concrete composites. However, due to the narrow voltage window resulting from measurements conducted under natural dry conditions (simulating real-world environments), the improvements in energy density and power density remained limited. The incorporation of IP concrete infill led to a 4.4–11.8% reduction in compressive strength, primarily attributable to interfacial defects and excessive ettringite formation within the LB matrix induced by the alkaline IP filler. Among the tested geometries, hexagonal cavities exhibited the smallest strength reduction (4.4%), maintaining a compressive strength of 13.55 MPa after filling. Furthermore, the system successfully powered an LED bulb for over 8 min, demonstrating its potential for low-power applications. This work offers a viable approach to manufacturing multifunctional structural energy storage devices using 3D printing, offering insights for the development of building-integrated energy storage systems.