High-performance spherical NiCo2S4 electrodes for all-solid-state cement-based hybrid battery-capacitor with moisture-regulated pore structure

With the growing demand for integrating energy storage into building materials, all-solid-state cement-based hybrid battery-capacitors (AC-HBCs) have emerged as a promising candidate due to their low cost and high safety. In this study, spherical NiCo 2 S 4 powder is synthesized via a hydrothermal method and fabricated into a NiCo 2 S 4 /nickel foam electrode, which delivers a high area capacity of 280.56 μAh·cm −2 at 0.2 mA·cm −2 . Asymmetric AC-HBCs are assembled using this electrode and a cement-6% PAA composite electrolyte. By optimizing the moisture content to tailor the pore structure of the electrolyte, a high ionic conductivity of 16.22 mS·cm −1 is achieved. The optimized device, PC-5, can operate at a notably high power density of 435.14 μW·cm −2 while delivering an energy density of 18.49 μWh·cm −2 . It also achieves a maximum area capacity of 42.50 μAh·cm −2 and demonstrates excellent stability, maintaining a coulombic efficiency above 98% over 3000 cycles. The device demonstrates practical viability by powering a small bulb and an electronic clock. This work provides a new avenue for applying cement-based hybrid battery-capacitors in civil engineering.