Direct current generation in triboelectric nanogenerators through ionic dynamics and electrode polarization effects

Efficient conversion of mechanical energy into direct current remains a significant challenge for current energy-harvesting devices. In ionic tribomaterials, the displacement and polarization of mobile ions can dynamically control both the magnitude and direction of generated charges. This process shares similarities with semiconductor-based tribovoltaic systems but differs from conventional dielectric triboelectric devices, where electrical conductivity and charge retention are often in competition. While ionic tribomaterials are receiving increasing attention, their ability to generate direct current directly from mechanical motion has not been fully investigated. Here, we show that incorporating ionic components, such as plasticizers, into a common dielectric polymer (polyvinyl chloride) transforms the output from alternating to direct current. This process is driven by contact electrification combined with electrode polarization, enabling stable direct current generation across contact-separation, sliding, and rotary motions-modes that are typically difficult to unify in a single design. The resulting devices maintain stable output under extended operation and varying environmental conditions, demonstrating a robust and versatile route for mechanical-to-electrical energy conversion. This approach bridges the performance gap between polymer-based triboelectric devices and tribovoltaic systems, offering a broadly applicable strategy for sustainable energy harvesting technologies.