Three-dimensional ordered macroporous NiFe2O4 coated carbon yarn for knittable fibriform supercapacitor

Binary metal oxides are considered as promising electrode materials due to the higher electrochemical activity than mono metal oxides. However, the poor conductivity and aggregation of binary metal oxides impede ion and electron transport kinetics, which deteriorates their electrochemical performances. Herein, we design and fabricate three-dimensional ordered macroporous NiFe2O4 on carbon yarn, in which a core of carbon yarn is covered with the sheath of three-dimensional ordered macroporous NiFe2O4. The three-dimensional ordered macroporous structure is feature with abundant transportation shortcuts for electrolyte ions and excellent structural stability, thus offering great advantages for efficient fibriform supercapacitor. The fibriform supercapacitor is further assembled using two intertwined three-dimensional ordered macroporous NiFe2O4-carbon yarn electrodes, both of which are solidified in the KOH-polyvinyl alcohol gel electrolyte. The assembled fibriform supercapacitor exhibits high specific capacitance (247 mu F cm(-1) at scan rate of 10mV s(-1)) and robust cycling stability (96% capacitance retention after 8000 cycles). Furthermore, the fibriform supercapacitor shows substantial mechanical flexibility with minor capacitance decrease upon continuous bending cycles, and the knitted fibriform supercapacitor exhibits the excellent wearability and integration. Thus, the as-prepared fibriform supercapacitor shows great promise as the energy storage unit for wearable electronics. (c) 2018 Elsevier Ltd. All rights reserved.