Graphene–Graphite Polyurethane Composite Based High‐Energy Density Flexible Supercapacitors

Abstract

Energy autonomy is critical for wearable and portable systems and to this end storage devices with high‐energy density are needed. This work presents high‐energy density flexible supercapacitors (SCs), showing three times the energy density than similar type of SCs reported in the literature. The graphene–graphite polyurethane (GPU) composite based SCs have maximum energy and power densities of 10.22 µWh cm −2 and 11.15 mW cm −2 , respectively, at a current density of 10 mA cm −2 and operating voltage of 2.25 V (considering the IR drop). The significant gain in the performance of SCs is due to excellent electroactive surface per unit area (surface roughness 97.6 nm) of GPU composite and high electrical conductivity (0.318 S cm −1 ). The fabricated SCs show stable response for more than 15 000 charging/discharging cycles at current densities of 10 mA cm −2 and operating voltage of 2.5 V (without considering the IR drop). The developed SCs are tested as energy storage devices for wide applications, namely: a) solar‐powered energy‐packs to operate 84 light‐emitting diodes (LEDs) for more than a minute and to drive the actuators of a prosthetic limb; b) powering high‐torque motors; and c) wristband for wearable sensors.

Flexible potentiometric pH sensors for wearable systems

“…Recent advances have witnessed the integration of wearable sensing platforms with wearable energy systems for power supply. 5,228 In our previous work, we developed a fully self-charging power pack (FSPP) for wearable applications (Fig. 8).…”

A Wearable Supercapacitor Based on Conductive PEDOT:PSS‐Coated Cloth and a Sweat Electrolyte

“…However, like conventional energy storage devices, these energy storage devices have used toxic electrolytes, which pose safety risk when used in wearable systems and require special packaging to prevent electrolyte leakages. [ 6,7 ] These issues could be addressed with biocompatible materials and the unique work presented with in the first instance demonstrating the use of biofluids such as sweat for the development of flexible SC.…”

Soft eSkin: distributed touch sensing with harmonized energy and computing

“…Similarly, the piezoelectric harvesters can be used to generate electricity as a result of multiple physical interactions or mechanical vibrations in the environment and use the same to fuel the low-power electronics in the eSkin. Likewise, the triboelectric nanogenerators (TENGs) working on the principle of energy generation under mechanical deformations such as pressing, touching, bending and stretching are most interesting for eSkin applications and have recently gained significant attention [38,[156][157][158]. In fact, a TENG based on single electrode with a load of 0.1 GΩ has been recently shown to deliver a power density of 500 mW m −2 by harvesting biomechanical energy for self-powered tactile sensor applications [156].…”

“…The harmonious integration of power with sensor on eSkin could be addressed with innovative multifunctional devices. For example, the changes in the chemical reaction in a supercapacitor (SC) under stress/bending could be exploited to develop an energy storage device as well as to measure the applied pressure [37,38]. Likewise, the changes in resonant frequency of an antenna (RFID) as a result of stretching or temperature variations could give an indication of strain or temperature [39].…”