All-Solid-State Flexible Asymmetric Supercapacitors Fabricated by the Binder-Free Hydrophilic Carbon Cloth@MnO2 and Hydrophilic Carbon Cloth@Polypyrrole Electrodes

Supercapacitors have attracted enormous attention for energy storage in both academic and industrial sectors in the past years. In this study, all-solid-state flexible asymmetric supercapacitors (ASCs) without any binder, incorporated with the hydrophilic carbon cloth (HCC) with MnO2 nanocomposite (HCC@MnO2) as the positive electrode, the HCC with polypyrrole (PPy) (HCC@PPy) as the negative electrode, and polyvinyl alcohol (PVA)-LiCl gel as both gel electrolyte and separator, are reported. The HCC@MnO2 and HCC@PPy electrodes are prepared by direct deposition of either MnO2 nanoparticles or PPy nanofilms on the HCC through a simple, facile, and controllable electrochemical deposition method, respectively. The HCC@MnO2 and HCC@PPy electrodes provide rich contact area for gel electrolyte, facilitating the rapid delivery of electrolyte ions, and also minimize the resistance of ASCs. As a result, all-solid-state flexible binder-free HCC@MnO2//HCC@PPy ASCs exhibit a large operating voltage of 1.8 V, high energy density of 28.2 Wh kg(-1) at the power density of 420.5 W kg(-1), and excellent cycling stability (91.2% capacitance retention after 5000 cycles). The present study provides a facile, scalable, and efficient approach to fabricate all-solid-state ASCs with high electrochemical storage performance for flexible electronics.