Enhancing the energy density of asymmetric stretchable supercapacitor based on wrinkled CNT@MnO2 cathode and CNT@polypyrrole anode.

With the advantages of high stickiness and stretchability of the hydrogel electrolyte as well as the resilient properties of film electrodes, the facile "prestrain-stick-release" strategy can be utilized for the assembly of a stretchable supercapacitor. Two major issues of concern are the relatively low mechanical strength of the hydrogel electrolyte and the low energy density of the assembled device. Herein, vinyl group grafted silica (CH2═CH-SiO2) nanoparticles were used as a nanoparticle cross-linker for polyacrylamide (PAAM), enhancing the tensile strength of 844 kPa at the strain of 3400% for the KCl-CH2═CH-SiO2/PAAM hydrogel electrolyte. Besides, carbon nanotube supported polypyrrole (CNT@PPy) and manganese dioxide (CNT@MnO2) film electrodes are prepared to assemble the stretchable asymmetric CNT@MnO2//KCl-CH2═CH-SiO2/PAAM//CNT@PPy supercapacitor, significantly enhancing the potential window to 0-2.0 V and achieving a high energy density of 40 Wh kg(-1) at the power density of 519 kW kg(-1) with the strain of 100%, which is the best known for the reported stretchable supercapacitors.