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 ((CoNi D ) 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 ∼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°, 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.