Flexoelectricity for green energy batteries

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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.