Understanding of the triboelectric charge accumulation from the view of materials plays a critical role in enhancing the output performance of triboelectric nanogenerator (TENG). In this paper, we have designed a feasible approach to modify the tribo-material of TENG by filling it with high permittivity nanoparticles and forming pores. The influence of dielectricity and porosity on the output performance is discussed experimentally and theoretically, which indicates that both the surface charge density and the charge transfer quantity have a close relationship with the relative permittivity and porosity of the tribo-material. A high output performance TENG based on a composite sponge PDMS film (CS-TENG) is fabricated by optimizing both the dielectric properties and the porosity of the tribo-material. With the combination of the enhancement of permittivity and production of pores in the PDMS film, the charge density of ∼19 nC cm(-2), open-circuit voltage of 338 V, and power density of 6.47 W m(-2) are obtained at working frequency of 2.5 Hz with the optimized film consisting of 10% SrTiO3 nanoparticles (∼100 nm in size) and 15% pores in volume, which gives over 5-fold power enhancement compared with the nanogenerator based on the pure PDMS film. This work gives a better understanding of the triboelectricity produced by the TENG from the view of materials and provides a new and effective way to enhance the performance of TENG from the material itself, not just its surface modification.

Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the investigation of polydimethylsiloxane-based composite film nanogenerators, indicating that the generator, in fact, acts as both an energy storage and output device. Maximum energy storage and output depend on the maximum charge density on the dielectric polymer surface, which is determined by the capacitance of the device. The effective thickness of polydimethylsiloxane can be greatly reduced by mixing a suitable amount of conductive nanoparticles into the polymer, through which the charge density on the polymer surface can be greatly increased. This finding can be applied to all the triboelectric nanogenerators with capacitor structures, and it provides an important guide to the structural design for nanogenerators. It is demonstrated that graphite particles with sizes of 20-40 nm and 3.0% mass mixed into the polydimethylsiloxane can reduce 34.68% of the effective thickness of the dielectric film and increase the surface charges by 111.27% on the dielectric film. The output power density of the triboelectric nanogenerator with the composite polydimethylsiloxane film is 3.7 W m(-2), which is 2.6 times as much as that of the pure polydimethylsiloxane film.

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external action, two triboelectric layers with opposite triboelectric charges periodically contact and separate from each other, which changes the induced potential difference between the two electrodes to drive an alternating current fl owing between the electrodes. For the previous TENGs, the two triboelectric layers are bonded to different objects, one of which needs to move working as the mechanical energy source. On the surface of the two triboelectric layers each is attached to a metal electrode and a conducting wire. Due to intertwinement of the wires in the moving process, such a device confi guration largely limits the multifunctionality and applicability of TENGs for harvesting energy. In addition, the interface between the metal electrodes and moving polymers are usually rough to increase friction charge density, which limits the operating life of the generators. Very recently, the freestanding-triboelectric-layer based nanogenerator without an attached electrode has been developed to solve these problems. [ 25,26 ] In reference to the planar TENGs, the previous devices could only harvest the kinetic energy along one direction, horizontally or vertically [ 23,27 ] or rotarily. [ 28,29 ] It is necessary that the structure of the TENGs' electrodes be improved so that they can harvest energy from all directions with advantages of being fl exible, light weight, durable, cost effective, and portable.Here, we develop a triboelectric generator based on a novel checker-like interdigital electrodes (TEGC) with a sandwiched polyethylene terephthalate (PET) thin fi lm between the sliding panel and electrodes that can harvest translational motion energy in all directions. Because the interdigital electrodes are divided into many regularly aligned pieces on each branch, a casual motion of the polytetrafl uoroethylene (PTFE) squares on the sliding panel in some direction can lead to a separation and contact of charges and thereby generate electricity. As the electrodes for charge transfer are in the same plane, the output electricity from the immovable electrodes is not affected by movement of the sliding panel. Electret PTFE fi lm is used for its high ability of holding charges (charge densities up to 5 × 10 −4 C m −2 with a theoretical lifetime of hundreds of years) and relatively high mechanical behavior. [ 8 ] The working current generating mechanism and performance in different A triboelectric generator based on checker-like interdigital electrodes (TEGC) with a sandwiched polyethylene terephthalate (PET) thin fi lm that can convert translation kinetic energy in all directions to electricity is reported. The design of the sandwiched PET thin fi lm can effectively avoid direct wear between metal electrodes and sliding panel. The mechanism of the TEGC is described in detail. The performance of the TEGC in different sliding directions is studied, indicating a maximum output power density of 1.9 W m −2 and open-circuit voltage of 210 V achieved in the X or Y sliding direction. The TEGC is used to charge a 110 µF co...