Kun Song,Rui Yang,Xiaoshuang Chen,Xin Wang,Guoli Chen,Nan Zhao
Developing electrodes with high stability and high specific capacity are two strategies to promote the application of supercapacitors. However, high specific capacity electrodes possess poor cycling stability, and good cycling performance electrode possesses low specific capacity, so it is difficult to achieve a balance. The stability of nano-sized metal oxides is reduced due to the collapse of their nanostructures during the cyclic process. Thus, the channel of electron transmission is destroyed, and the conduction of charge is not smooth. Therefore, we select electrodes with highest specific capacity and better cycling performance from many structures of CoFe 2 O 4 electrodes that are controllable designed by solvent ratio and structure-directing agent, such as chain, sphere, box, belt etc. In addition, we use an electrochemical method to coat the electrode with a layer of PEDOT to increase the conductivity and cyclic stability for practical application. Hence, the NF/CoFe 2 O 4 sphere/PEDOT as cathode indicates an outstanding specific capacity of 299.2 mAh g −1 at 1 A g −1 . The energy density is 230.4 Wh kg −1 (power density of 616 W kg −1 ). The aqueous hybrid supercapacitor shows a good cycle life, after 2000 cycles the capacity retention is 91.7%. The maximum current and self-discharge phenomena of mechanical energy charging are also studied and it is demonstrated that it has good tolerance to large current, which is suitable for mechanical energy charging.
Poly(3,4-ethylenedioxythiophene) (PEDOT) coating is advantageous in constructing flexible sensors, due to its good flexibility, high conductivity, and excellent physical and chemical stability. Traditional solution-based coating methods, however, are difficult to retain the micro- and nanostructures of the substrates, thus decreasing the sensitivity of the resulted sensors. In this work, we prepared superhydrophobic (SHB) strain sensors using a piezoresistive composite made from consecutive vapor deposition of conformal polymer coatings , i.e. PEDOT and poly(perfluorodecyl acrylate- co -ethylene glycol diacrylate) on fabrics using oxidative and initiated chemical vapor deposition methods. Compared with the pristine fabric sample, the composite materials displayed significantly improved initial currents, which are attributed to more conductive paths created by PEDOT coating. The resulted strain sensor displayed great flexibility, large sensitivity, wide sensing range, and excellent reliability. Furthermore, the sensor has been successfully employed to monitor various human motions in real time. The hydrophobic outer layer endows the sensor self-cleaning and durability capacities, indicating possible applications under harsh environment.
The vanadium oxyhydroxide has attracted considerable attention as a cathode in aqueous zinc-ion batteries due to its changeable morphology and high theoretical capacity. However, poor conductivity and structural disintegration limit its further application. Herein, we prepare VOOH nanoparticles and apply them onto carbon cloth, followed by coating with poly(3,4-ethylenedioxythiophene) (VOOH@PEDOT). The PEDOT coating layer and carbon cloth substrate significantly mitigate volume change and enhance electrode conductivity during cycling. Benefiting from the improved charge transfer and structural stability, the optimized VOOH@PEDOT displays an excellent discharge capacity of 230 mA h/g and good cycle stability over 500 cycles at 1 A/g. Additionally, the energy storage mechanism is elucidated through ex-situ XRD analysis.
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