Boosting Contact Electrification by Amorphous Polyvinyl Alcohol Endowing Improved Contact Adhesion and Electrochemical Capacitance

Abstract

AbstractIon conductive hydrogels are relevant components in wearable, biocompatible, and biodegradable electronics. Polyvinyl‐alcohol (PVA) homopolymer is often the favored choice for integration into supercapacitors and energy harvesters as in sustainable triboelectric nanogenerators (TENGs). However, to further improve hydrogel‐based TENGs, a deeper understanding of the impact of their composition and structure on devices performance is necessary. Here, it is shown how ionic hydrogels based on an amorphous‐PVA (a‐PVA) allow to fabricate TENGs that outperform the one based on the homopolymer. When used as tribomaterial, the Li‐doped a‐PVA allows to achieve a twofold higher pressure sensitivity compared to PVA, and to develop a conformable e‐skin. When used as an ionic conductor encased in an elastomeric tribomaterial, 100 mW cm−2 average power is obtained, providing 25% power increase compared to PVA. At the origin of such enhancement is the increased softness, stronger adhesive contact, higher ionic mobility (> 3,5‐fold increase), and long‐term stability achieved with Li‐doped a‐PVA. These improvements are attributed to the high density of hydroxyl groups and amorphous structure present in the a‐PVA, enabling a strong binding to water molecules. This work discloses novel insights on those parameters allowing to develop easy‐processable, stable, and highly conductive hydrogels for integration in conformable, soft, and biocompatible TENGs.