Redox-active potassium iodide boosts ion storage efficiency in solid cementitious electrolyte toward energy-storing concrete

Journal article, 2026

Concrete-type supercapacitor (CTS) can store electrical energy in structural materials to achieve zero energy consumption and intelligence in building facilities. However, their low electrical conductivity and tortuous porosity hinder ion conduction and the formation of double electric layers, thereby limiting the power density and charge-discharge efficiency of traditional CTS. In contrast, CTS based on cementitious solid electrolyte rely on redox reactions in the electrolyte for energy storage, with less dependence on electrode materials. Moreover, they lock the liquid through a polymer network, featuring non-volatility and leak-proof properties, making them suitable for large-scale building applications. Herein, we develop a novel cement-based solid electrolyte composed of Portland cement (PC), polyacrylic acid (PAA), and potassium iodide (KI). The I- /IO3- redox couple in KI can undergo rapid and reversible Faraday reactions at the electrode surface, providing additional pseudocapacitance. Additionally, the addition of KI increases the total ion concentration in the electrolyte, enabling more effective formation of continuous ion transport channels in the concrete pores, thereby reducing the bulk resistance of the electrolyte and the electrode/electrolyte interface resistance, achieving a significant ionic conductivity of 15.2 mS cm- 1. As a result, the specific capacitance of CTS based on the PC/PAA/KI electrolyte increased to 122.78 F g- 1, with a capacitance retention rate of 89.1% after 5000 cycles. Furthermore, the compressive strength of this structure is as high as 13.1 MPa, highlighting the practical application potential of this hybrid system in civil buildings and providing a sustainable path for the development of green, low-carbon, and self-powered building solutions.