Progress in techniques for improving the output performance of triboelectric nanogenerators

As a new technology based on the combined effects of contact electrification and electrostatic induction, triboelectric nanogenerators (TENGs) are already widely studied for energy harvesting and novel sensor design. In recent years, with the progress of material synthesis and device technology, researchers have been developing various working mechanisms and designs to enhance the output performance of TENGs. In this review, the research advance in improving the output performance of TENGs through different strategies is comprehensively reviewed. The main contents of this review include three aspects: surface material modifications of TENGs, mechanical design, and power management. Firstly, the basic principles and working modes of TENGs are introduced. Secondly, the surface material selection and treatment methods of TENGs are classified. According to the different treatment methods, the modification methods of surface materials are divided into physical and chemical modifications. Meanwhile, the production of high-performance degradable materials is considered to enhance the performance of TENGs, including cellulose-based materials, artificial polymer materials and bio-based materials. Then, the methods for improving the output power of TENGs through mechanical design are classified, including multilayer structures, TENG networks and adjusting the mechanical motion frequency of TENGs. In addition, the existing methods for improving the power supply efficiency of TENGs by using switch management are summarized. Power management methods are classified according to the types of switches, including mechanical switches and electronic switches. Finally, based on the current progress, we discuss the critical problems and systematically suggest future research directions and challenges. Enhancing the output performance of triboelectric nanogenerators through surface modification, mechanical design and power management.