All‐Solid‐State Flexible Asymmetric Supercapacitors Fabricated by the Binder‐Free Hydrophilic Carbon Cloth@MnO 2 and Hydrophilic Carbon Cloth@Polypyrrole Electrodes

Abstract 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 MnO 2 nanocomposite (HCC@MnO 2 ) 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@MnO 2 and HCC@PPy electrodes are prepared by direct deposition of either MnO 2 nanoparticles or PPy nanofilms on the HCC through a simple, facile, and controllable electrochemical deposition method, respectively. The HCC@MnO 2 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@MnO 2 //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.