Cellulose melt processing assisted by small biomass molecule to fabricate recyclable ionogels for versatile stretchable triboelectric nanogenerators

Highlights: • A recyclable double-network ionogel with multiple functions was fabricated by novel melt-polymerization of hydroxypropyl cellulose in molten α-lipoic acid. • A TENG based on ionogel displayed good performances even after stretching, high temperature storage, long-term operation, mechanical damage, and recycling. • The applications of TENG in green power supply and self-powered sensors were demonstrated. Ionogels are promising electrode materials of stretchable triboelectric nanogenerators (TENG). However, the development of ionogel materials that simultaneously meet the requirements of green start feedstock, simple fabrication, multifunction, and recyclable feature remains a challenging issue. Here, we try to address this by adopting novel melt-polymerization of hydroxypropyl cellulose (HPC) in molten α-lipoic acid (LA) liquid. This strategy is extremely simple, facile, based on biomass molecules, and offers a promising methodology to completely melt processing of cellulose materials. The HPC chains successfully forms the double-network structure with LA poly(disulfides) chains by multiple hydrogen bonding interactions. As result, the integrated merits of high transparency, high strength, fine stretchability, moderate conductivity, healability, ultraviolet resistance, thermal stability, strain-sensitivity, and full recyclability are realized in the obtained ionogels. Encouraging by these features, a versatile triboelectric nanogenerator (I-TENG) (3 cm × 3 cm) is fabricated using ionogels as functional electrodes. This nanogenerator can harvest biomechanical energies and convert them into electrical outputs of 80 V, 2 µA, 27 nC, and the max power density of 67.9 mW m⁻² at a fixed frequency of 3 Hz, respectively. Beside transparent characteristic, this nanogenerator is able to maintain good energy harvesting performance after stretching, high temperature storage, long-term operation, mechanical damage, and even recycling. Notably, the I-TENG can not only work as green power supply to drive small electronics, but also as self-powered sensors to distinguish human motions and English letters.