Triboelectric nanogenerators (TENGs) are promising energy-harvesting devices that can reduce the carbon footprint and prevent global warming. Although extensive research has been conducted on TENGs, they have a serious limitation in that they can only generate a low peak current output. To overcome this limitation, direct-current TENGs (DC-TENGs) based on electrostatic discharge have been studied, which can increase the electrical output with an enhanced charge density or amplify the current output with an electron avalanche effect. However, these DC-TENGs can only generate short-duration peak outputs, where the integral of these outputs is low; thus, it is difficult to charge commercial capacitors or batteries, which narrows the application field of TENGs. In this regard, a loop-structured film-capacitor direct-current TENG (LFD-TENG) that can accumulate polarized charges inside the loop-structured film capacitor and harvest electricity from the discharge was fabricated. With the accumulated charges, the LFD-TENG can generate a long-duration high-peak output compared to general DC-TENGs, which significantly increases the peak voltage, root mean square voltage, and transferred charge. The high-performance LFD-TENG was demonstrated to power 3000 light-emitting diodes (LEDs), 11 5 W LEDs, and a continuously operated thermo-hygrometer.