Effect of pump voltage on triboelectric properties and air breakdown of sliding-mode triboelectric nanogenerator

The surface charge density of vertical contact-separation-mode triboelectric nanogenerator (CS-TENG) can be significantly enhanced using charge pumping strategy. However, for lateral sliding-mode triboelectric nanogenerator (LS-TENG), the triboelectric effect is accompanied by material wear, and the electric field in the contact gap can be distorted by charged debris, so it remains unclear about the impact of pump voltage on the triboelectrification effect and air breakdown behavior. In this paper, the influence of pump voltage on the triboelectric properties of CS-TENG and LS-TENG under dry friction is studied, and then the effects of lubrication by squalane on the tribological and electrical properties of LS-TENG is explored. The results indicate that the threshold of pump voltage for air breakdown is dependent on the working mode of TENG. Specifically, in CS-TENG, the threshold of pump voltage aligns with Paschen's law, whereas in LS-TENG, it is deviates from this law. For LS-TENG, as the pump voltage increases, the electrical output initially decreases and subsequently increases, which is attributed to the adsorption of the transfer film by the electric field generated by the pump voltage. When the pump voltage increases further until air breakdown occurs between the contact surfaces, the charge density decreases again. At this stage, the transfer film at the friction interface is destroyed by air breakdown, leading to intensified wear, surface degradation, and reduced durability of the LS-TENG. The addition of an appropriate amount of squalane to the contact interface effectively prevented the formation of the transfer film, thereby enhancing durability. Moreover, squalane suppresses the air breakdown by filling the air gap and forming a lubrication film with high dielectric constant, which significantly improved the electrical output of the TENG. This study provides theoretical insights and guidance for the design of LS-TENG under charge pump with improved durability and electrical performance.