Flexoelectricity for green energy batteries
Lead Research Organisation:
Imperial College London
Department Name: Mechanical Engineering
Abstract
The booming development of innovative technologies, such as portable electronics and sensors, is increasing the demand for renewable power supplies. To meet this demand triboelectric nanogenerators (TENGs) have been recently proposed. TENGs are green energy-harvesting devices that convert mechanical energy into electricity by coupling triboelectricity and electrostatic induction. They can charge batteries and provide energy to self-powered electronics and sensors used for a wide range of applications. This versatility makes TENGs key devices to replace fossil energy and drive the green transition.
Their application, however, still faces limitations because once the electronic saturation point is reached the electric output starts to decrease. EXCITON aims at enhancing TENGs performances by exploiting electromechanical effects such as flexoelectricity. Flexoelectricity refers to the generation of electric polarization caused by strain gradients, which are large at the nanoscale and in flexible 2D and polymeric materials, widely used in TENGs fabrication.
These effects are strongly enhanced in tribological contact, where high non-uniform stresses can be exploited to increase the electric output and TENGs performance. Indeed, it has been recently suggested that flexoelectricity drives triboelectrification.
Providing a fundamental understanding of the interplay between flexo and triboelectricity, EXCITON aims to determine a sound method to permanently improve TENGs performances. I will evaluate the effect of non-uniform deformations on the tribocharging of 2D and polymeric materials by combining ab-initio DFPT and experimental tribometric and KPFM measurements of the electromechanical and triboelectric properties of these materials. The combined theoretical/experimental approach will allow to establish a new protocol for the studies in the field and will constitute a first step towards the application of the outcomes.
Their application, however, still faces limitations because once the electronic saturation point is reached the electric output starts to decrease. EXCITON aims at enhancing TENGs performances by exploiting electromechanical effects such as flexoelectricity. Flexoelectricity refers to the generation of electric polarization caused by strain gradients, which are large at the nanoscale and in flexible 2D and polymeric materials, widely used in TENGs fabrication.
These effects are strongly enhanced in tribological contact, where high non-uniform stresses can be exploited to increase the electric output and TENGs performance. Indeed, it has been recently suggested that flexoelectricity drives triboelectrification.
Providing a fundamental understanding of the interplay between flexo and triboelectricity, EXCITON aims to determine a sound method to permanently improve TENGs performances. I will evaluate the effect of non-uniform deformations on the tribocharging of 2D and polymeric materials by combining ab-initio DFPT and experimental tribometric and KPFM measurements of the electromechanical and triboelectric properties of these materials. The combined theoretical/experimental approach will allow to establish a new protocol for the studies in the field and will constitute a first step towards the application of the outcomes.
Publications
Fatti G
(2025)
First-Principle Insights into Positive Triboelectrification of Polyoxymethylene Through Homolytic Bond Rupture
in Nanoenergy Advances
Fatti G
(2023)
Rational Design Strategy for Triboelectric Nanogenerators Based on Electron Back Flow and Ionic Defects: The Case of Polytetrafluoroethylene
in Advanced Electronic Materials
| Description | Triboelectricity, the phenomenon behind static electricity generated by rubbing or contact between two materials, is one of the oldest observed scientific problems, yet it remains poorly understood. This lack of understanding makes it difficult to control triboelectric outputs, significantly impacting the development and efficiency of numerous applications, particularly in energy harvesting technologies. Triboelectricity can indeed be used to accumulate charges on surfaces in contact and, through suitable electrodes, power electronic devices. The fellowship funded through this award aimed at investigating the relationship between triboelectricity and flexoelectricity-a related effect where non-uniform deformation within a material generates electric polarization and internal electric fields that can promote the transfer of electrons at materials' interfaces. Through this research, we have developed a robust, first-principles-based methodology to systematically study the triboelectric phenomenon. Crucially, the workflow created is structured to allow reproducible application even by non-specialists, significantly enhancing accessibility and fostering broader scientific exploration. This methodology represents a substantial advance in how researchers can approach the complex interactions driving triboelectric effects at a fundamental level. Our results reveal important insights: for materials with a high dielectric permittivity, flexoelectricity alone can act as a primary driver sufficient to trigger triboelectric charge generation. However, in most cases analyzed, flexoelectricity facilitates but does not independently enable charge separation. This finding highlights a key open research question moving forward: understanding precisely how flexoelectricity interacts with other potential drivers of triboelectric charge generation. The methodology was developed in close collaboration with Professor Massimiliano Stengel's group at the Universitat Autònoma de Barcelona, Spain. Prof Stengel's strong theoretical background allowed us to bridge the gap between theoretical advances and practical engineering applications. Additionally, computational results from this project enabled the establishment of a new collaboration with Professor Zhong Lin Wang's group, which leads the world's largest research group focused on triboelectricity and its applications. Finally, throughout the development of this methodological workflow, the fellow acquired advanced skills in first-principles computational techniques and became proficient in applying the theoretical framework of polarization theory. These new capabilities significantly enhance future research potential and contribute to a deeper understanding of complex material phenomena. In summary, this fellowship has provided significant advances in understanding the triboelectric phenomenon, created a broadly accessible methodological tool, identified new research questions, and facilitated key international collaborations. |
| Exploitation Route | The outcomes of this fellowship provide a pathway for future academic and industrial applications. Academically, the newly developed methodology and workflow offer researchers a robust tool to investigate triboelectric phenomena at a fundamental level. Research groups specializing in materials science, applied physics, and computational chemistry are expected to leverage these results to explore and identify new materials with optimized triboelectric properties. Collaborations with prominent groups, such as those led by Professors Massimiliano Stengel and Zhong Lin Wang, ensure the continuous evolution and refinement of the methodology, further expanding its impact within the international scientific community. From a non-academic perspective, industries focused on energy harvesting and renewable energy technologies could directly benefit from these findings. At the moment, triboelectric nanogenerators are not commercially viable. Companies interested in developing them can utilize the insights established by this research to enhance device performance, durability, and predictability. This has the potential to significantly advance the commercial viability of TENG-based solutions for self-powered electronics and wearable devices. Finally, the accessible nature of the developed methodology means it can be effectively adopted by industrial R&D departments, facilitating innovation and accelerating technology transfer between academia and industry. |
| Sectors | Aerospace Defence and Marine Digital/Communication/Information Technologies (including Software) Electronics Energy Healthcare Manufacturing including Industrial Biotechology Transport |
| Description | Collaboration with Professor Zhong Lin Wang - Director, Beijing Institue of Nanoenergy and Nanosystems, Chinese Academy of Sciences, China. |
| Organisation | Beijing Institute of Nanoenergy and Nanosystems |
| Country | China |
| Sector | Public |
| PI Contribution | We have recently established a strong link with Professor Wang and his team to work on triboelectricity and TENGs - our team looks at the theoretcial aspects. |
| Collaborator Contribution | Idea exchanges and experimental techniques |
| Impact | Research that may impact both new devices in healthcare and energy harvesting |
| Start Year | 2025 |