Abstract:

Objective MXene and aramid nanofibers (ANFs) have similar surface polarity and good compatibility. Preliminary experiments show that with an optimal blend ratio of ANFs to MXene, excellent wet spinning processability and good conductivity can be achieved. When the mass ratio of ANFs to MXene is 1:4, the conductivity of A1M4 (with a mass ratio of ANFs to MXene at 1:4)composite fibers produced by wet spinning can reach 3 145.82 S/m. However, the fiber strength is not yet ideal for practical applications. Coaxial wet spinning has better designability compared to the conventional wet spinning. In order to fully leverage the advantages of the excellent skeleton reinforcement performance of ANFs, further balance the contradiction between the electrical and mechanical properties of ANFs/MXene fibers, and to improve the comprehensive performance of fiber electrodes, 1:4 blend ratio of ANFs to ANFs/MXene was adopted to prepare single (core/shell) layer materials, through adjusting the distribution position and concentration of ANFs reinforced skeleton by wet spinning forming method. A flexible fiber electrode with excellent mechanical and electrochemical comprehensive properties was designed and prepared, aiming for applications in the field of flexible supercapacitor energy storage.
Method A series of coaxial fiber electrodes was designed and parepared using the wet spinning method. By systematically analyzing the microscopic physical and chemical structures, mechanical properties, electrical and electrochemical properties of various coaxial fiber electrode samples, the feasibility of this technology approach in designing and preparing flexible fiber electrodes was explored.
Results For A-AM (coaxial fibers with ANFs as shell layer and ANFs/MXene composites as core layer) coaxial fibers, by adjusting the concentration of shell ANFs, it was found that when increasing the concentration of shell ANFs, the compactness of the shell aggregation structure was increased, the mechanical strength was improved, but the conductivity was decreased. Among them, the sample A-0.7-AM (coaxial fiber with a concentration of shell ANFs at 0.7%) demonstrated that failure strength and modulus reached 98.57 MPa and 5.25 GPa, respectively, which are 99.37% and 15.89% higher than those of A1M4 composite fibers. As for A-AM coaxial fibers, ANF fiber bundles were found partially "overflowing" to the shell layer in all samples, which blocked the AM conductive pathway in the shell layer to a certain extent. The conductivity was reduced to varying degrees compared to A1M4 composite fibers, but it was indeed beneficial for improving mechanical strength. Among them, the mechanical strength and modulus for AM-A-1.5 (coaxial fiber with a concentration of core ANFs at 1.5%) were 110.98 MPa and 5.28 GPa, respectively, representing an increase of 124.47% and 16.53% compared to A1M4 composite fibers. The electrochemical performance tests indicated that at a current density of 0.2 A/g, the specific capacitance is the most prominent for sample A-0.5-AM (coaxial fiber with a concentration of shell (ANFs at 0.5%), reaching 310.59 F/g. Sample AM-A-1.5 exhibited battery type electrode characteristics, with a specific capacitance of up to 120.10 F/g.
Conclusion A series of coaxial fiber electrodes were prepared using AM blends with a ratio of 1:4 of ANFs to ANFs/MXene as single (core/shell) layer materials. By adjusting the distribution position and concentration of ANFs reinforced skeleton, the synergistic effect of the materials was well exerted, balancing the contradiction between mechanical, electrical, and electrochemical properties, and demonstrating good application prospects.

Key words: MXene, aramid nanofiber, electrode material, fiber electrode, supercapacitor