Co-Electrodeposited porous PEDOT–CNT microelectrodes for integrated micro-supercapacitors with high energy density, high rate capability, and long cycling life

Abstract

Recently, conducting polymers (CPs) have gained significant attention for their potential applications in micro-supercapacitors (MSCs). Prior to actualizing this potential, however, several critical issues should be resolved, notably their low cycling stability and comparatively low capacitance and energy density. Concurrently, challenges remain in improving the performance of CPs for use in MSCs in terms of their electrical conductivity, energy density, and cycling stability. For this investigation, we fabricated a high-performance MSC based on poly(3,4-ethylenedioxythiophene) (PEDOT)-coated multi-walled carbon nanotube (MWCNT) nanoporous network microelectrodes by photolithography combined with electrochemical co-deposition on micro-current collectors. We then sought to confirm the proposed higher electrochemical performance of this hybrid MSC with the synergetic effect of PEDOT as a pseudo-capacitive material and MWCNTs as electric double-layer capacitive material. As reported herein, the hybrid MSC delivers a maximum specific capacitance of 20.6 mF cm⁻² (82.4 F cm⁻³) and, consequently, a comparatively high areal energy density of 2.82 μW h cm⁻² (11.4 mW h cm⁻³) in a wide voltage window of 1.0 V at a current density of 0.1 mA cm⁻², and a maximum power density of 18.55 W cm⁻³ at an energy density of 8.1 mW h cm⁻³. Furthermore, the MSC displays remarkable long-term cycling stability, retaining 99.9% of its initial capacitance after 20 000 CV and GCD cycles with a coulombic efficiency of 100%. Additionally, two PEDOT–CNT MSCs are coupled in series to power a red light emitting diode. The results provided herein confirm that the PEDOT–CNT MSCs exhibit improved performance over other CP based MSCs.