Boosting volume energy density in structural energy supercapacitors via highly interconnected porous cement-based electrolytes

Cement-based supercapacitors (CBSCs) represent a pioneering strategy for integrating load bearing and energy-storage functions within construction materials, addressing both the growing demand for renewable energy storage and the urgent need for construction-sector decarbonisation. In this study, a highly interconnected, low-tortuosity porous cement-based electrolyte is developed by coupling hydrogen peroxide (H₂O₂)–driven chemical foaming with polyvinyl alcohol/sodium alginate (PVA/SA) crosslinking, effectively overcoming the inherent trade-off between ionic transport efficiency and mechanical strength in the cementitious systems. The resulting hierarchical porous network exhibits a high porosity of 42%, a reduced tortuosity of 2.8, and a 46.3% enhancement in pore connectivity, collectively facilitating efficient and rapid ion migration. Consequently, the new cement-based electrolyte achieves a high ionic conductivity of 15.6 mS cm −1 while maintaining a compressive strength of 21.9 MPa, outperforming previously reported porous cement-based electrolytes. When assembled into a CBSC device, the system delivers an excellent specific capacitance of 560.4 mF cm −3 and retains 87.3% of its initial capacitance after 2000 charge–discharge cycles, demonstrating good electrochemical stability. Furthermore, the optimized electrolyte enables an energy density of 77.8 Wh m −3 , sufficient for a medium-sized building wall to power a typical household for nearly one-third of a day. Overall, the findings provide an innovative yet practical pathway toward self-powering, energy-efficient, and low-carbon building components, supporting the development of next-generation net-zero civil infrastructure.