Flexible and Conductive Carbonized Cotton Fabrics Coupled with a Nanostructured Ni(OH)₂ Coating for High Performance Aqueous Symmetric Supercapacitors

Flexible and wearable supercapacitor (SC) fabrics have received considerable research interests recently. However, their high hydrophobicity, poor conductivity, inferior capacitance, and low energy density remain a bottleneck to be solved. Herein, a highly flexible and conductive carbonized cotton fabric (CCF) covered by a unique nanostructured Ni­(OH)₂ layer is fabricated via a facile high-temperature carbonization process, followed by an electrochemical deposition (ED) treatment. The nanostructured Ni­(OH)₂ greatly improves the hydrophilicity of CCF to promote electrolyte penetration and offers abundant electroactive sites, leading to dramatically increased specific capacitance and operating potential window (OPW). The resultant Ni­(OH)₂­@CCF is then applied as the electrode for an aqueous symmetric SC device. This device has an OPW of 1.4 V and exhibits a high specific capacitance of 131.43 F g^–1 at the current density of 0.25 A g^–1 with a high energy density (35.78 Wh kg^–1 at a power density of 0.35 kW kg^–1, and it can reach 18.28 Wh kg^–1 at a high power density of 14.00 kW kg^–1), which outperforms the performance of most aqueous symmetric SCs. In addition, the SC demonstrates excellent capacitance stability under various bending conditions, suggesting its potentials in flexible and wearable energy-storage devices.