Buildings as Energy Storage Solutions
Researchers from Harbin Institute of Technology and the Chinese Academy of Sciences have made significant strides in the realm of construction materials, developing an innovative cement-based substance that not only provides structural support but also possesses the ability to store and distribute electrical energy. In light of the ongoing global energy crisis, nations worldwide are actively seeking alternatives to enhance energy sustainability. Among the options being investigated is the creation of multifunctional building materials that can simultaneously bear loads and store electrical energy.
Experts in the field assert that these next-generation materials could expand the role of civil infrastructure in strategies aimed at ensuring energy supply while accelerating the transition towards renewable sources.
Challenges in Large-Scale Production
Nevertheless, the mass production of cement-based energy storage devices designed for integration within architectural structures presents numerous challenges. A primary hurdle lies in ensuring the components responsible for storing and distributing electricity remain affixed to the load-bearing elements, such as cement. Additionally, it is crucial to ensure that the ionisation process occurs without interference within the materials, a condition necessary for maintaining storage efficiency.
A recent study published in ACS Nano tackled these issues by designing an experimental 3D-printed cement supercapacitor that demonstrated its ability to store electricity without compromising the concrete’s structural integrity during laboratory tests. Unlike traditional batteries that rely on chemical reactions for energy storage and release, supercapacitors operate on electrostatic principles, accumulating electrical charges on the surface of their electrodes.
Understanding Supercapacitor Functionality
This fundamental difference impacts their operation; batteries typically store more energy for prolonged periods, while supercapacitors can charge and discharge much more rapidly. Consequently, they prove advantageous in scenarios where substantial amounts of electricity are needed in a short timeframe. Moreover, supercapacitors endure significantly more charge and discharge cycles before their performance deteriorates.
Utilising this principle, the researchers crafted a supercapacitor using a direct ink writing technique, which allows for the deposition of materials in a specific pattern. This method proved instrumental in overcoming challenges related to effective ionisation and the adhesion of components that impede the development of multifunctional building materials.
Innovative Conductive Ink Composition
The team formulated a conductive ink comprising carbon nanotubes, carbon black, and traditional cement. This combination not only facilitates energy storage but also mitigates the risk of separation between the components. Subsequently, the mixture was printed onto a concrete slab in an interdigitated pattern, akin to two hands with interlocking fingers that do not touch.
This configuration maintained the necessary proximity and separation between the electrodes to promote the ionisation process, while also preventing energy performance from declining as the material thickness increased.
Laboratory Results and Mechanical Properties
In laboratory tests conducted within a one-volt operating range, the supercapacitor achieved a surface capacitance of 162.14 millifarads per square centimetre, measured with a current of 0.46 milliamperes per square centimetre. Capacitance indicates the amount of electrical charge a device can store for a given voltage. Additionally, it recorded a surface energy density of 22.52 microwatt-hours per square centimetre, representing the quantity of energy it can store relative to its surface area. The device also attained a power density of 0.49 milliwatts per square centimetre, indicating the speed at which it can deliver the stored electricity.
Regarding the mechanical properties necessary for construction applications, the researchers found that the material boasts a compressive strength of 23 megapascals, comparable to that of commercial concrete used in elements such as stairs and slabs.
Future Prospects and Limitations
While the development presents promising advancements, the researchers acknowledge existing limitations. The recorded strength values do not confirm that the material is suitable for use in all buildings or structural elements. Furthermore, the supercapacitor’s performance significantly diminishes at temperatures of -18 °C, and the team does not rule out potential alterations in its behaviour under high humidity conditions.
Despite these challenges, the authors believe their work represents a notable advancement that could, in the future, broaden the functions of urban infrastructure and help tackle the energy crisis. Jing Zhong, a researcher at Harbin Institute of Technology and lead author of the study, concluded, “If building materials could not only support structures but also store energy, perceive their environment, and even interact with people, buildings would evolve beyond mere passive shelters. They could transform into genuinely intelligent environments.”