Cotton textile enabled, all-solid-state flexible supercapacitors†
Abstract
A hierarchical NiCo2O4@NiCo2O4 core/shell nanostructure was grown on flexible cotton activated carbon textiles (ACTs) to fabricate NiCo2O4@NiCo2O4/ACT electrodes. After dipping with PVA/KOH polymer gel which served as both the solid state electrolyte and separator, the flexible NiCo2O4@NiCo2O4/ACT hybrid electrode exhibited an exceptional combination of electrochemical and mechanical properties in terms of specific capacitance (1929 F gā1, based on the mass of NiCo2O4), energy density (83.6 Wh kgā1), power density (8.4 kW kgā1), cycling stability, and mechanical robustness (the tensile strength is 6.4 times higher than that of pure ACT). The outstanding electrochemical performance is ascribed to the unique core/shell nanostructure with high active-surface area, morphological stability, and short ion transport path. Such hierarchical core/shell nanostructure of the same material on a cotton-enabled flexible substrate should inspire us to develop flexible solid-state textile energy storage devices for future wearable electronics.