Interfacial Polarization Engineering via One‐Dimensional Ionic Crystal Fibers for High‐Performance Triboelectric and Piezoelectric Nanogenerators

Enhancing the dielectric properties of polymer composites through particulate inorganic fillers 0D has been widely explored as an effective strategy to improve the energy-harvesting performance of triboelectric and piezoelectric devices. Compared with conventional particulate fillers, 1D fillers offer intrinsic structural anisotropy and enlarged polymer-filler interfaces that favor interfacial polarization and charge transport. However, the intrinsically isotropic crystallization behavior of inorganic salts hinders the formation of long-range ordered 1D structures, leaving one-dimensional inorganic salt fibers largely unexplored as functional fillers. Here, we propose a template-guided directional crystallization strategy to construct 1D potassium chloride (KCl) fibers as functional fillers. The resulting fibers reach macroscopic lengths of up to ∼6 cm and retain continuous crystalline morphology within polymer matrices, thereby enabling extended polymer-filler interfaces. As a result, the fiber-based composites exhibit enhanced dielectric performance over particle-filled composites. Multi-scale characterization reveals that the 1D fibrous structure promotes interfacial polarization and guides dipole alignment within the polymer matrix. Furthermore, the fiber-enhanced PENG was integrated into a wearable sensing platform for real-time monitoring and recognition of human motion with machine learning. This work demonstrates that one-dimensional inorganic salt fibers, as functional fillers, provide an effective strategy for enhancing interfacial polarization in flexible energy-harvesting systems.