Self-standing porosity modulated carbon-based membrane electrodes for high energy-power flexible pseudocapacitors

In response to the increasing demand for portable electronics, flexible supercapacitors have garnered substantial attention over a decade. Herein, we report an innovative route for fabrication of self-standing, flexible, electrically conductive, and porosity-modulated carbon-based membrane (PMCM) electrodes using regenerated networked cellulose (NC) with carbon nanostructures (CNS). Through systematic inclusion of various amounts of PVP within the NC/CNS mixture, we attained adaptable porosities (8, 15, 18, and 25 %), offering a versatile framework for devising self-standing electrodes with customized structural properties. All the as-prepared PMCM electrodes were then probed under various physiochemical characterizations in aqueous electrolyte (0.5 M H₂SO₄) and it was revealed that the PMCM-electrode with the highest porosity of 25 % (PMCM-25 %) has displayed lowest charge transfer resistance (R_ct) thereby delivering very high specific capacitive (295 F g⁻¹ at 50 mV s⁻¹ (0.75 F cm²) and 292 F g⁻¹ at 0.5 A g⁻¹). Further, the PMCM-25 % electrode exhibited a cyclic retention of 90.5 % after 10,000 charge-discharge CV cycles and delivered a high energy-power density (26 Wh kg⁻¹ and 4600 W kg⁻¹, respectively) in a symmetric device configuration. The PMCM-25 % electrode has demonstrated remarkably low electronic resistivity (1.8 × 10⁻⁴ Ω m) and exceptional electronic conductivity (5 × 10³ S m⁻¹) as determined by the Kelvin technique. Moreover, the aforementioned optimum electrode can withstand a high stress of 4.3 K Pa with 0.43 % elongation at break (under uniaxial tensile tests) and have proven to be suitable for integrating into irregular surfaces, paving the way for modern flexible supercapacitors.