Silver nanoparticles as a conductive bridge for high-performance flexible all-solid-state asymmetric supercapacitor

Summary With the rapid development of portable electronic devices, it is strongly urgent to explore the flexible and sustainable supercapacitor with lightweight, large power/energy density, good cycle stability, outstanding coulombic efficiency, and excellent operational safety. Herein, a novel and flexible all-solid-state asymmetric supercapacitor is assembled from silver (Ag) or/and cobalt acid nickel (NiCo 2 O 4 ) nanoparticles coated with hollow carbon micro-skeleton (HCMS-Ag and HCMS@NiCo 2 O 4 -Ag). The HCMS@NiCo 2 O 4 -Ag electrode is subsequently prepared by a facile hard template combined with hydrothermal method. The morphology analysis shows that plenty of NiCo 2 O 4 nanoflowers composed of a tremendous number of nanoneedles are uniformly grown on the three-dimensional hollow carbon micro-skeleton. This unique and novel structure endows the prepared electrode with a high specific capacitance of 527.4 F g −1 at a current density of 0.5 A g −1 and outstanding rate capability of 75%. The assembled pliable asymmetric supercapacitor possesses a maximum energy density of 42.67 Wh kg −1 , long cycle life (97.4% capacitance retention), and excellent flexibility. Therefore, this work opens new horizon to develop the next-generation carbon composites for flexible all-solid-state asymmetric supercapacitor with high levels of electrochemical properties.