关键词: 石墨烯纤维, 高应变, 加捻, 超级电容器, 电化学

Abstract: With the increasing advancement of the smart wearable industry, there is a growing demand for flexible energy supply devices and human movement monitoring devices with excellent mechanical flexibility. Graphene fibers are of great interest to research workers because of their great potential in areas such as sensors, supercapacitors, and electric heating. However, in the previous reports, graphene-based materials as macro-structural components had low strain. For this purpose, some scholars have compounded graphene with other fibers to prepare graphene composite fibers. Although the resulting graphene composite fibers are improved in strain, they often lack electrical or electrochemical properties. These affect their applications in wearable and other fields requiring high strain.
To prepare pure graphene fibers with high strain and high electrochemical properties, we prepared graphene fibers with homogeneous texture by wet-spinning technology, and then made them into graphene yarns with dense twisted layered structure by the twisting method. Then, we studied the mechanical properties, electrical conductivity, microstructure, chemical structure and electrochemical properties of the yarns. The results show that the elongation at break reaches 11.3%, the tensile strength reaches 90 MPa, and the conductivity reaches 53.8 S/cm. On this basis, the graphene yarns were transformed into flexible supercapacitors. It is found that the obtained yarn supercapacitors have the characteristics of controllable structure. The dense yarn structure is conducive to the rapid transmission of electrolyte ions within the yarn and between the electrolytes. The supercapacitors have high specific capacitance (48.06 mF/cm2) and a long cycle life (with capacitance retention of 85%-90% of after 10,000 charge-discharge cycles). The results show that the prepared graphene yarn has high resistivity, excellent electrical conductivity and good electrochemical performance.
The graphene yarns with twisted structure prepated in this paper has high strain and excellent electrochemical performance, is applicable to such fields as flexible sensors and fiber supercapacitors, and has great promise in energy storage applications and wearable devices.

Key words: graphene fibers, high strain, twisting, supercapacitor, electrochemistry