Ionic thermoelectric effect inducing cation-enriched surface of hydrogel to enhance output performance of triboelectric nanogenerator

Abstract

The most robust consensus related to ionic-hydrogel-based triboelectric nanogenerator (TENG) is that the charge density at the solid interface plays a pivotal role in its output performance. However, there has been no reliable evidence of the mechanism regarding the influence of ion enrichment on TENG. Higher surface charge density at the solid interface could result in higher output performance. Herein, the ionic hydrogel is prepared through polymerization reaction of the organic monomers with LiCl as the ionic conductor. The ion migration on the hydrogel surface is regulated via tuning the temperature difference between the top and bottom sides. Upon contacting with the upper electrode, more induction charges are induced on the cation-enriched surface of hydrogel, leading to a larger output of the TENG. At the temperature difference of 25 °C, the open-circuit voltage and maximum output power density is increased by 77% and 166% compared with the TENG without temperature field, respectively. When the temperature of the hydrogel surface is higher than 50 °C, the output performance of TENG would decrease due to the water loss of hydrogel. This research will advance further understanding of the mechanism of thermoelectric ionic conductors in TENGs, self-powered sensors, and wearable devices.