Ionic liquid-based molecular design for transparent, flexible, and fire-retardant triboelectric nanogenerator (TENG) for wearable energy solutions

Abstract

Transparent and flexible triboelectric nanogenerator (TENG) represent an efficient and invisible energy solution for generating eco-friendly electricity from mechanical human motion for wearable electronic devices and systems. In addition to boosting the output performance of TENG, the molecular design relying on non-flammable materials and anti-ignition invulnerability should be considered when designing TENG devices, to ensure the safety of personnel working under extreme temperature conditions. However, the requirement for nonflammability of conventional transparent triboelectric materials in wearable applications remains either unmet or almost unexamined to date. Here, we propose bi-continuous and flame-retarding epoxy-based ion-gel films that retain mechanical flexibility, optical transparency, and fast ionic polarization for high-performance and deformable TENG. It is found that our transparent and flexible TENG devices produce an output voltage and current as high as approximately 150 V and 45 mu A, respectively, from an external mechanical stimulus while also retaining their fire retardancy and low flammability. This TENG is not flammable even after 20 s of trying, whereas conventional triboelectric materials were completely burned by the fire under the same conditions. Therefore, we propose that our synergistic design of triboelectric ion-gel films, including fire-retardant epoxybased dual cation-incorporated ionic liquid, represents a significant step toward a high-performance, durable, and transparent wearable energy solution.