ZnO–Plasma Polymer Fluorocarbon Thin Films for Stable Battery Anodes and High-Output Triboelectric Nanogenerators

In this study, ZnO–plasma polymer fluorocarbon (PPFC) nanocomposite thin films were prepared by a mid-range frequency sputtering method using ZnO–polyfluoroethylene–carbon nanotube hybrid targets, and their optical, physical, and surface properties were investigated as functions of the ZnO concentration in the targets. The obtained films exhibited excellent visible light transmittance and hydrophobic characteristics, while their surface roughness and refractive index increased with increasing the ZnO concentration from 6.52 to 15.3 nm and from 1.45 to 1.55, respectively, due to the larger number of ZnO-related absorption states. In addition, the structures and compositions of the films were determined by X-ray diffraction (XRD), grazing incidence small-angle X-ray scattering (GISAXS), and X-ray photoelectron spectroscopy (XPS). It was found that mixed ZnO nanoparticles were well embedded into the PPFC matrix. Finally, we examined the potential applicability of the fabricated ZnO–PPFC nanocomposite thin films in various fields, such as batteries and triboelectric nanogenerators (TENGs). The TENG output voltage increased by approximately 15.8% from 28.05 V for commercial polytetrafluoroethylene (PTFE)-based generators to 32.48 V for the ZnO–PPFC nanocomposite film-based TENG. Furthermore, the ZnO–PPFC nanocomposite thin film demonstrated a stable performance as a battery anode material. While the output of a ZnO reference electrode decreased by approximately 74.5% after 100 cycles, the output of a ZnO–PPFC anode decreased by only 12.4% and remained stable afterward.