Textile-based electronics hold great promise as they can endow wearable devices with soft and comfortable characteristics. In this work, a multifunctional conductive yarn was fabricated by coating a commercial regenerated cellulose (lyocell) yarn with polypyrrole (PPy). The method is simple, low-cost, and highly scalable and it endows the common lyocell yarn with flame-retardant as well as good electrical heating properties and excellent electrochemical performance. The PPy-coated lyocell yarn (PCLY) behaved as a regular yarn and could be hand-knitted into a full fabric. The PCLY fabric demonstrated high conductivity, allowing its use as a wearable Joule heater. The polypyrrole coating significantly improved the limiting oxygen index (LOI) of the lyocell yarn from 21.7% to 40.2%, endowing the yarn with an excellent flame-retardant property. PCLY was stitched into a fabric to form interdigitated electrodes and further assembled into flexible textile micro-supercapacitors. The resulting device with 10 interdigitated electrodes exhibited high areal specific capacitance of 663 mF cm⁻² and energy density of 21.6 μW h cm⁻² at 1 mA cm⁻². Furthermore, six devices in series could power a blue light-emitting-diode (LED) of 3 V for more than 30 seconds. This facile fabrication provides novel and practical insights toward wearable textile-based electronics.

In this study, a kind of inorganic composite flame retardant (Sep@Fe₂O₃) was prepared by combining solution deposition and calcination methods using sepiolite microfiber material as carrier. This inorganic compound flame retardant was combined with waterborne polyurethane (WPU) through layer-by-layer method to prepare WPU composites. The SEM and EDS, TEM, and XRD were used to characterize the microscopic morphology and crystal structure of WPU composites. Thermogravimetric analysis tests confirmed the good thermal stability of WPU/Sep@Fe₂O₃ composites; at the temperature of 600C, the carbon residual percentage of WPU/Sep, WPU/Fe₂O₃, and WPU/Sep@Fe₂O₃ composites is 7.3, 12.2, and 13.4, respectively, higher than that of WPU (1.4). Vertical combustion tests proved better flame-retardant property of WPU/Sep@Fe₂O₃ composite-coated cotton than noncoated cotton. The microcalorimeter test proved that the PHRR of WPU/Sep@Fe₂O₃ composites decreased by 61 compared with that of WPU. In addition, after combining with Sep@Fe₂O₃, the breaking strength of WPU increased by 35.