Electromechanical modeling for triboelectric nanogenerators considering the distribution of polymer transfer film

When there exits continuous dry friction between the metal electrode and the polymer in the working process of triboelectric nanogenerators (TENGs), the polymer will suffer serious wear, and the wear debris adsorbed to the surface of metal electrode will form the transfer film, resulting in the decrease in electrical output. However, the quantitative relationship between wear characteristics and electrical output still remains unclear. In this paper, a charge density-dependent wear model for rotary freestanding TENG (RF-TENG) is established first, and then the numerical algorithms such as augmented Lagrange algorithm and Newton Rapson iterative method are employed to investigate the mapping relationship between the mass loss and the transfer film area fraction. Next, an electrostatic induction model considering the distribution of transfer film for RF-TENG is presented in combination with Monte Carlo random sampling, and the quantitative relationship between the transfer film area fraction and the electrical output is explored. The results show that, the transfer film area fraction increases first and then remains almost unchanged with the increasing mass loss of polymer; the increase in the transfer film area fraction causes the triboelectric charge density to decay, and the decay rate decreases gradually because the growth rate of transfer film area fraction decreases. The larger electrostatic force resulting from larger charge density will aggravate the polymer wear and intensify the attenuation amplitude of electrical output. This study can reveal the mapping relationship between polymer wear and electrification performance of TENGs, thus providing a theoretical basis for the design of TENGs with high durability and stability.