Interconnected Conductive Networks in Cement Mortar Enable High-Performance Structural Supercapacitors

Integrating energy storage capabilities into construction materials offers a promising pathway toward multifunctional, self-sustaining infrastructure. Among various approaches, cement-based supercapacitors (CSCs) are particularly attractive due to their inherent compatibility with structural elements, safety, and long cycle life. However, achieving both robust mechanical strength and high electrochemical performance in realistic mortar systems containing aggregates remains a major challenge. Here, we report a scalable design strategy that enables the fabrication of structurally sound and electrochemically active cement mortar electrodes. By incorporating reduced graphene oxide (rGO)-coated conductive aggregates into a carbon nanotube (CNT)–reinforced cement matrix, a three-dimensional hybrid conductive network is formed within the mortar. This architecture enhances charge transport while preserving mechanical integrity. Compression forming and low water-to-cement ratios further reduce porosity, enabling high-performance electrodes with flexural and compressive strengths of 9.72 MPa and 32.22 MPa, respectively—comparable to conventional cement mortars. The resulting symmetric device delivers a volumetric capacitance of 350.0 mF cm⁻³, energy density of 48.5 μWh cm⁻³, and power density of 32.8 mW cm⁻³, with excellent cycling stability (∼100 % retention over 10,000 cycles). This work demonstrates a practical and scalable pathway to multifunctional cement-based materials, opening new possibilities for embedding energy storage into structural components.