Fabrication of a 2.8 V high-performance aqueous flexible fiber-shaped asymmetric micro-supercapacitor based on MnO2/PEDOT:PSS-reduced graphene oxide nanocomposite grown on carbon fiber electrode

Abstract

Flexible and lightweight fiber-shaped micro-supercapacitors have attracted tremendous attention as next-generation portable electronic devices, due to their high flexibility, tiny volume, and wearability. Herein, we successfully fabricated a ternary binder-free nanocomposite of MnO₂/PEDOT:PSS–rGO on a carbon fiber substrate for application in high performance fiber-shaped micro-supercapacitors. The synergistic effects of the different components in the fiber-shaped electrode help to deliver a high specific capacitance of 2.9 F cm⁻² (194 F cm⁻³ and 550 mF cm⁻¹) at a current density of 5 mA cm⁻² and a long cycle life with 95% capacitance retention after 5000 cycles in 1 M Na₂SO₄ electrolyte. A fiber-shaped asymmetric micro-device based on the resulting hybrid electrode was assembled. A maximum energy density of E_A = 295 μW h cm⁻² (E_V = 19 mW h cm⁻³) and power density of P_A = 14 mW cm⁻² (P_V = 930 mW cm⁻³) were achieved in an operating voltage window of 0–2.0 V in a solid-state Na₂SO₄–CMC electrolyte. Moreover, a fiber-shaped asymmetric micro-device with a super-concentrated potassium acetate-based water-in-salt electrolyte (27 m KOAC) is presented. The use of the water-in-salt electrolyte enables a cell voltage of 2.8 V, and energy densities are higher than those of the micro-device operating with conventional dilute aqueous electrolytes.