Enhancement of output charge density of TENG in high humidity by water molecules induced self-polarization effect on dielectric polymers

Abstract

Although utilizing charge excitation is an effective strategy to achieve high charge density for triboelectric nanogenerators (TENGs), the conductive pathways formed by water molecules in a high-humidity environment cause inevitable output charge decay and limit practical applications of TENGs. Herein, a self-polarization effect-based charge-excitation TENG (SP-CE-TENG) is proposed with high surface charge density (SCD), and the charge self-increase phenomenon of dielectric materials with different strong polar groups is investigated. It is found that the unique strong polarization characteristics of water molecules further promote the self-polarization process of dielectric materials with the increase in humidity. As a result, an ultra-high SCD of 2.88 mC m−2 is obtained in the atmosphere with 40% relative humidity (RH) using 7 µm homemade poly(vinylidene fluoride-trifluoroethylene) film. Meanwhile, the effective SCD of the SP-CE-TENG maintains more than 1.92 mC m−2 even at 90% RH, which is the highest charge density for TENGs in a high humidity environment. This work presents a practical approach to boosting the output charge density of TENGs, which is helpful for in-depth exploration of the polarization behaviors of polar molecules in a high-humidity environment.