Enhanced electrochemical performances of graphene based solid-state flexible cable type supercapacitor using redox mediated polymer gel electrolyte

The flexible cable/wire type supercapacitors are attracting more attentions as the power supply in wearable electronics. Herein, we report the flexible cable-type supercapacitor (FCSC) using hydrothermally reduced graphene oxide (rGO) nanosheets and successfully improved their electrochemical performances using redox additive electrolyte. The synthesized rGO nanosheets are well characterized in both structural and electrochemical parts. The fabricated FCSC device works up to 1 V without any evolution occurred, and exhibits excellent electrochemical performances. Further, the performances of FCSC are improved more than three times using sodium molybdate (Na₂MoO₄) as redox additive electrolyte. The addition of Na₂MoO₄ in polymer gel electrolyte for rGO based FCSC exhibits a maximum length capacitance and energy density of 18.75 mF cm⁻¹ (areal capacitance of 38.2 mF cm⁻²) and 2.6 μWh cm⁻¹ (areal energy density of 5.3 μWh cm⁻²) respectively. The detailed mechanism has been explored for these improved electrochemical activities. The flexibility and stability of the FCSC device have been investigated and three serially connected devices are capable of lit up the green and blue LEDs. Overall, these findings could open up a simple and cost effective approach to improve the performances of carbon materials in the field of flexible energy storage applications.