Snowflake-Like Dendritic CoNi Alloy-rGO Nanocomposite as a Cathode Electrode Material for an All-Solid-State Flexible Asymmetric High-Performance Supercapacitor Device

Flexible all-solid-state supercapacitors having high mechanical stability and foldable features are crucial to meet the growing demands for a large number of portable electronic devices such as wearable electronics, displays, touch screens, detectors, etc. Here, we report the fabrication of such a flexible all-solid-state asymmetric supercapacitor device by using a nanocomposite composed of a snowflake-like dendritic CoNi alloy and reduced graphene oxide ((CoNiD)(60)-rGO(40)) as the positive electrode and pure rGO as the negative electrode for the first time. In this device, a polyvinyl alcohol (PVA) gel containing 3 M KOH and 0.1 M K-4[Fe(CN)(6)] was used as the electrolyte cum separator. This supercapacitor device offers a high energy density value of 52.8 Wh kg(-1) at a power density of 2000 W kg(-1). The values of these two key performance parameters are superior to the many commercially available supercapacitors and reported values in the literature. In addition, this device also exhibits retention of similar to 95% of its initial specific capacitance value after 4000 cycles at a current density of 2.5 A g(-1), displaying its high cycling stability. This supercapacitor is so flexible that no mechanical deformation occurs even after bending at different angles and folding up to 180 degrees, and its specific capacitance value practically remains unaffected when the device was twisted at different bending angles. This flexible all-solid-state asymmetric supercapacitor device can power a light-emitting diode (LED) and demonstrates its promise to meet the practical applications in energy storage technology.