TECH
Cement-based supercapacitors could power next-generation ‘smart’ buildings
Imagine a future in which the very concrete beneath your feet and around your windows does more than hold a building upright. In that future, the same material that forms slabs, stairs, and load-bearing walls also stores the electricity generated by rooftop solar panels, releasing it in bursts to light corridors, run sensors, and keep emergency systems alive during outages. That vision moved a significant step closer to reality with the publication of a peer-reviewed study in ACS Nano, in which researchers report an efficient, energy-storing cement supercapacitor that, crucially, performs as well as commercial concrete in mechanical tests.
The work, led by corresponding author Jing Zhong together with colleagues Wencai Ren and Haiping Wu, demonstrates that cement need not be a passive, inert filler in the built environment. Instead, it can be engineered into an active electrochemical component, one that is 3D printable, structurally robust, and capable of powering real electronic devices.
To understand why this result matters, it helps to distinguish supercapacitors from the lithium-ion batteries that dominate consumer electronics. Batteries store large amounts of energy through slow chemical reactions, which is why they take hours to charge and degrade over hundreds or thousands of cycles. Supercapacitors, by contrast, store energy electrostatically, in the electric field that forms at the interface between an electrode and an electrolyte.
They hold relatively small amounts of energy compared with batteries, but they take that energy in and release it extremely rapidly, and in some designs they can survive millions of charge-discharge cycles without significant degradation. That combination of speed and durability makes them attractive for applications where power is needed in short, repeated bursts rather than as a long-duration reserve. For a building fitted with solar panels, supercapacitors embedded in the structure could absorb surges of renewable electricity as they arrive and discharge them on demand, smoothing the mismatch between when energy is generated and when it is actually used.
The central challenge in turning cement into a supercapacitor is that ordinary concrete is a poor electrical conductor. Cement hydrates into a porous, mineral-rich matrix that is excellent at bearing compressive loads but terrible at shuttling electrons and ions. The research team’s solution was to build conductivity directly into the material. They mixed carbon nanotubes, carbon black, and cement together to form a printable electrode ink. Carbon nanotubes are cylindrical structures of carbon atoms just nanometers in diameter, renowned for their exceptional electrical conductivity and mechanical strength. Carbon black, a much cheaper amorphous form of carbon, provides additional conductive pathways and helps form a percolating network throughout the composite. Blended into wet cement, these carbon additives transform the paste from an insulator into an electrode material, while the cement itself continues to cure and harden much as it would in any construction application.
Geometry proved to be just as important as chemistry. Using a 3D printer, the team deposited the electrode ink onto a small concrete slab in a pattern resembling interlocked fingers, a configuration known in electrochemistry as an interdigitated electrode design. In this arrangement, two sets of parallel electrode fingers alternate with one another, like the interlaced fingers of two hands held together without touching. The significance of this geometry lies in the distance that charged ions must travel. In a conventional two-plate capacitor, ions in the electrolyte have to migrate across the entire gap separating the electrodes, which slows the device down and wastes energy as internal resistance. With interdigitated electrodes, every finger of one polarity sits immediately adjacent to fingers of the opposite polarity, so ions move only short distances laterally. As the researchers note, this shortened travel distance made the overall supercapacitor more efficient than previous iterations of cement-based energy storage, which had struggled with exactly this ionic transport bottleneck.
A remarkable feature of the design is that the electrolyte is not added as a separate liquid component but arises from the cement itself. As the cement within the slab hydrated, the chemical reaction that gives concrete its strength, its pores filled with water and dissolved ions that could easily travel between the electrodes. In other words, the very process that turns printable ink into hardened concrete simultaneously creates the ionic medium the supercapacitor needs to function. This monolithic approach, in which electrode, electrolyte, and structural support are one continuous piece of material, is what the study’s title refers to in describing monolithic 3D-printed interdigitated cement-based supercapacitors for structural energy storage. It eliminates the interfaces and packaging that complicate conventional devices and means the energy-storage function can, in principle, be printed wherever a builder wants it within a larger concrete element.
Of course, an energy-storage device embedded in a building is useless if it compromises the building’s safety. Concrete in structural applications must meet strict compressive strength standards, and any multifunctional material has to prove it can carry loads without failing. The researchers therefore subjected their cement supercapacitor to mechanical testing and found that its compressive strength was comparable to that of commercial concrete used in slabs and stairs. This is the result that elevates the work from a laboratory curiosity toward practical relevance. Previous attempts at cement-based energy storage often faced a trade-off, in which adding conductive carbon or porosity weakened the material. Here, the team achieved a device that is simultaneously an electrode, an electrolyte-filled capacitor, and a structural material meeting the expectations placed on ordinary construction concrete.
The researchers also demonstrated that their devices do real electrical work. Three supercapacitors printed on the same slab and wired together successfully powered a small array of LEDs, a modest demonstration on its own but an important proof of concept showing that multiple devices fabricated from a single concrete element can be connected into a functioning energy system. Looking ahead, the team envisions these supercapacitors powering everything from emergency lighting to self-powered sensors. That second application deserves particular attention. Modern buildings increasingly depend on distributed sensor networks that monitor temperature, occupancy, air quality, and structural health, and wiring or periodically replacing batteries for thousands of such sensors is costly and cumbersome. Sensors embedded in or on concrete that draw their operating power from the concrete itself would remove that maintenance burden entirely, enabling dense, self-sustaining monitoring of the built environment.
Like any emerging technology, the cement supercapacitor has identified limits, and the team was candid about one of them. The devices operated stably under moderate heating and cooling, but at around zero degrees Fahrenheit, or minus 18 degrees Celsius, their performance started to wane. This matters because the electrolyte in the system is water-based, arising from the hydration of the cement, and water loses its ionic mobility as it approaches freezing. In cold climates, where buildings must perform year-round, a supercapacitor that fades in deep winter would be a serious limitation. The researchers state that future research will focus on fortifying the supercapacitors against cold-weather conditions, an engineering challenge that will likely involve strategies to keep the pore solution ionically active at low temperatures. It is a reminder that multifunctional materials must satisfy the demands of every function they take on, including environmental resilience across the full range of conditions a building experiences.
The broader implications reach toward what researchers call smart buildings, structures that generate, store, and manage energy within their own fabric. As Jing Zhong explains, if building materials could not only support structures but also store energy, sense their surroundings, and even interact with people, buildings would become more than passive shelters. They could become truly smart environments. The study, published in ACS Nano under the title Monolithic 3D-Printed Interdigitated Cement-Based Supercapacitors for Structural Energy Storage, was supported by funding from the Guangdong Hailong Construction Technology Company Limited, a subsidiary of China State Construction International Holdings Limited, an indication that the construction industry itself sees commercial potential in structural energy storage.
Considerable work remains before supercapacitor walls appear on job sites, including scaling from small slabs to full structural elements, integrating renewable generation and power electronics, and solving the cold-weather performance gap. But the foundational demonstration is now on the table: a cement-based supercapacitor that stores energy efficiently, prints into interdigitated geometries, powers LEDs, and matches commercial concrete in compressive strength. The walls of future buildings may not merely shelter their occupants. They may quietly hold the charge that keeps those buildings alive.
