Research On Flexible Supercapacitors For Wearable Electronic Devices

Supercapacitors, as new energy storage devices between traditional electrochemical batteries and conventional capacitors, have attracted growing attention because of their high power density, fast charging and discharging rates, long cycle life and environmental friendliness. In order to meet the development needs of portable, wearable electronic devices, flexible solid-state supercapacitors are becoming the focus of current research. In this Master thesis, we focused on the design and synthesis of CNT/MnO2 NT, CNT@PPy and AgNW/WO3 hybrid electrodes, and deeply explored their applications in flexible energy storage devices and flexible electrochromic devices. The main work and conclusions are listed below:1. CNT/MnO2 NT hybrid electrodes were designed and synthesized by employing a facile vacuum-filtering method, and their freestanding structure effectively guaranteed the superior flexibility and excellent electrochemical performance. Flexible solid-state supercapacitor devices were assembled by using the as-prepared CNT/MnO2 NT hybrid electrodes, and the devices exhibited a high energy density of 0.45 mWh/cm3 while the power density is 13.8 mW/cm3. In addition, a prototype of flexible watch band was manufactured by connecting four supercapacitor devices in series, and successfully powered an electronic watch for a long time, demonstrating their potential applications in wearable and portable electronic equipment.2. Electrochemical active materials PPy was successfully loaded on the surface of CNT with a stable core-shell structure by a simple electrochemical polymerization deposition process. The as-prepared CNT@PPy electrodes demonstrated significantly enhanced mechanical properites(the ultimate tensile strength is as high as 16 MPa) and greatly improved electrochemical performance(5.6 times larger areal capacitance than CNT electrode) because of the synergistic effects between CNT and PPy. All-solid-state flexible supercapacitor devices were fabricated with the robust CNT@PPy electrodes, and the devices exhibited high electrochemical performance(a total device volumetric capacitance of 4.9 F/cm3 at 0.05 A/cm3) and execllent long cycle life(95% capacitance retention after 10000 cycles).3. AgNW/WO3 flexible electrochromic supercapacitor hybrid electrodes were designed and prepared by employing novel AgNW based flexible transparent conducting substrates. The systematic test characterization exhibited that the as-prepared electrode have an outstanding optical properties(the light transmittance can be reduced to 11.8% from the initial 55.9% at 633 nm while the coloration efficiency can be up to 80.2 cm2/C) and great capacitance(13.6 mF/cm2), which effectively promote the development of novel smart flexible equipment combining electrochromism and energy storage.