High-Performance, Highly Stretchable, Flexible Moist-Electric Generators via Molecular Engineering of Hydrogels.

Harvesting energy from ubiquitous moisture has emerged as a promising technology, offering opportunities to power wearable electronics. However, low current density and inadequate stretching limit their integration into self-powered wearables. Herein, a high-performance, highly stretchable, and flexible moist-electric generator (MEG) is developed via molecular engineering of hydrogels. The molecular engineering involves the impregnation of lithium ions and sulfonic acid groups into the polymer molecular chains to create ion-conductive and stretchable hydrogels. This new strategy fully leverages the molecular structure of polymer chains, circumventing the addition of extra elastomers or conductors. A centimeter-sized hydrogel-based MEG can generate an open-circuit voltage of 0.81 V and a short-circuit current density of up to 480 µA cm -2 . This current density is more than ten times that of most reported MEGs. Moreover, molecular engineering improves the mechanical properties of hydrogels, resulting in a stretchability of 506%, representing the state-of-the-art level in reported MEGs. Notably, large-scale integration of the high-performance and stretchable MEGs is demonstrated to power wearables with integrated electronics, including respiration monitoring masks, smart helmets, and medical suits. This work provides fresh insights into the design of high-performance and stretchable MEGs, facilitating their application to self-powered wearables and broadening the application scenario.