This study presents a high-performance electrospun nanocomposite membrane composed of poly (vinylidene fluoride) (PVDF) and different phases of titanium dioxide (TiO₂) for liquid–solid triboelectric nanogenerator (LS-TENG) applications. To address the low surface charge density and dielectric constant of pristine PVDF, anatase and rutile TiO 2 nanoparticles were incorporated into the polymer matrix through electrospinning, which promoted the formation of the electroactive β-phase essential for enhancing triboelectric performance. Among them, rutile TiO₂ at 5   wt% significantly promoted the formation of the electroactive β-phase (up to 87.6%), resulting in an eightfold enhancement in electrical output compared to the pure PVDF membrane. The optimized nanogenerator achieved an output voltage of 6.9   V, a current of 71.03 μA, and a peak power density of 0.55   W/m². A cascaded TENG architecture was further developed by stacking multiple nanocomposite membranes, effectively amplifying output through sequential liquid–solid contact. The resulting device demonstrates excellent energy conversion efficiency, long-term stability, and strong sensitivity to fluid flow and pH changes, highlighting its potential for self-powered sensing and environmental monitoring. This work provides a scalable strategy for designing electrospun functional composites for advanced triboelectric energy harvesting applications.