Flexible and Weaveable Wire-Shaped Capacitor with Ultra-High Energy Density

Abstract

Wearable electronics and microelectronics have been shown to be highly desired in the current and further life. To power these wearable electronic systems, flexible energy storage devices are needed. Comparing with the conventional planar device architectures, one-dimensional fiber micro-supercapacitors (FSCs) with the merits of lightweight, tiny volume, high flexibility and weavability which can be directly used as wearable components are more attractive. However, compared with batteries or traditional capacitors, FSCs show much lower-energy density and suffer from extra challenges in mechanical performance. According to the equation (E = 0.5CU2), energy is proportional to capacitance. So it is crucial to explore high capacitance fibers with good mechanical properties for FSCs. Electric-double layer capacitors (EDLCs) store energy through the charge separation at the electrode/electrolyte interface. In our study, we try to increase the capacitance and energy density of EDLCs by increasing the fiber interfacial area. We adopt a simple pipe mold method to fabricate hollow RGO/PEDOT composite fibers and hollow pure RGO fibers (labeled as HCFs and HPFs) with excellent flexibility and conductivity. Furthermore, the hollow fibers show a dramatic charge-storage ability. The symmetric solid-state FSCs composed of two HCFs reveal a high specific areal capacitance of 304.5 mF cm-2 at 0.08 mA cm-2, corresponding to an ultra-high energy density of 6.8 µWh cm-2 at a power density of 16.6 µW cm-2. To the best of our knowledge, it is the highest record for FSCs to date. In this presentation, we will discuss the fiber formation mechanism, charge storage mechanism and we will display the flexible wire-shaped energy device constructed by the one-dimensional fiber micro-supercapacitors.