Kosmotropic ions embedded hydrogel for significantly enhancing deformability and performance of iontronic triboelectric nanogenerators

Abstract

Hydrogels are adaptable ionic conductors for a wide range of soft devices, attracting attention in triboelectric nanogenerators (TENGs) for their potential to provide stretchable TENGs. Nonetheless, hydrogels' mechanical and output performance degrades in dry circumstances, restricting their use. Here, we use the kosmotropic effect to enable hydrogels to retain stable mechanical properties under dry conditions while simultaneously enhancing their power generation performance in TENGs. The kosmotropic hydrogel demonstrates an extraordinary ability to maintain stable triboelectric output under dry conditions. Among the kosmotropic ions studied, sulfate and sulfite-based ions (SO42-and SO32-) were identified to be more effective in generating a surface charge-blocking layer through crystallization, leading to improved charge retention and triboelectric output among the investigated kosmotropic in optimizing internal structure and interfacial charge dynamics, ion selection is crucial. As a result, the kosmotropic iontronic hydrogel-based TENGs significantly suppresses parasitic charge dissipation, resulting in a 3-fold increase in power density compared to conventional designs even under arid conditions. Furthermore, the kosmotropic iontronic hydrogel-based TENG could be stretched up to 700 % of its original length, representing a 2.3-fold improvement compared to untreated hydrogels. This study introduces hydrogels with improved mechanical and electrical stability for TENGs, enabling their use in real-world applications.