Polyelectrolytes as a Stable and Tunable Platform for Triboelectric Nanogenerators.

Polyelectrolytes (PEs) provide a versatile material system for improving the efficiency and stability of triboelectric nanogenerators (TENGs). Compared to conventional ionic liquids (ILs), which suffer from leakage, environmental instability, and limited durability, PEs feature covalently tethered ionic groups that enable precise tribopolarity control while preventing unwanted ion migration. By systematically varying polymer backbones and ionic compositions, including two polycations and three polyanions, tunable triboelectric behavior is demonstrated using Kelvin Probe Force Microscopy, time-of-flight secondary ion mass spectrometry, and TENG output measurements. The polymethyl acrylate (PMA)-based polycation with 20% ion inclusion shows strongly tribopositive behavior, producing 83 V compared to 45 V for PMA. The polystyrene (PS)-based polyanion with 10% ion inclusion exhibits strongly tribonegative behavior with 34 V, compared to 8 V for PS. Optimizing ion ratios enhances charge retention by suppressing excessive ionic conduction. The mechanical and thermal stability of PEs is demonstrated by output measurements over time; for example, the short-circuit current of PMA-based polycation with 20% ion inclusion remains nearly unchanged after 1 week at 60 °C, in contrast to an ≈27% drop observed in a polymer-IL system (poly(methyl methacrylate) with 10 wt% IL). These findings highlight the suitability of PEs as a robust, stable, and tunable platform for next-generation energy-harvesting applications.