The ability of future electronics to derive operational power from the working environment is attractive for realizing self-powered unattended electronics. Triboelectric nanogenerator (TENG) effectively harvests the otherwise wasted ubiquitous mechanical energy. Despite the recent advances in the design and development of various triboelectric devices, these devices' output still falls short in meeting the practical needs of directly powering electronics and sensors. Here, we review the recent progress in the design and optimization strategies for improving the TENG output performance, including but not limited to theoretical simulation, materials engineering, device engineering, and power management. The ubiquitous applications of the TENGs in micro/high-voltage power source, multifunctional intelligence, blue energy harvesting, and selfpowered electrochemical system are also discussed. Finally, we provide our perspectives regarding the challenges and opportunities for the future development of triboelectric devices with engineered high-performance and designer functionalities.