Direct-current triboelectric nanogenerators (DC-TENGs), which are used in smart electronics and energy storage, have attracted tremendous scientific interest owing to their rectification-free and high energy utilization efficiency. In this study, the authors propose a new type of DC-TENG that operates in the contact–separation mode with a unique adhesive–conductive interface for the first time. The results demonstrate that the TENG output increases with increasing interfacial adhesion strength; both the adhesive polymer and conductive tribomaterial are essential factors for the DC output. The proposed mechanism is based on mechanoion generation via covalent bond cleavage during material transfer and the charge leakage effect. Specifically, the DC-TENG exhibits unique frequency-decreasing and force-enhancing output characteristics. It can directly drive LEDs or charge commercial capacitors. By integrating a stretchable electrode, an adhesive-based single-electrode TENG can be used as a strain sensor or material detector. This work presents a new type of DC-TENG with a conventional two-electrode configuration and provides new perspectives on the fundamental research and applications of DC-TENGs.