Graphene fiber-based supercapacitors are known as the potential energy resources for wearable/flexible electronics. However, increasing their specific capacitance and energy density remains a significant challenge. This paper indicates a double layer capacitance of the graphene nanosheets accompanied by pseudocapacitive behavior of the polyaniline to prepare composite fibers with high capacitive response. The polyaniline/graphene composite fibers (PANI/GFs) were synthesized by the self-assembled strategy and chemical reduction by HI. The wrinkle architecture of graphene nanosheets and uniform dispersion of the polyaniline are beneficial to increase the internal electroactive sites and provide a stable structure for the composite fibers. The constructed fiber-shaped supercapacitors with solid-state electrolyte deliver an excellent areal specific capacitance of 370.2 mF cm⁻² and an outstanding areal energy density of 12.9 μW h cm⁻². The current work reveals the attractive potential of the as-synthesized composite fibers for constructing fiber-shaped supercapacitors with distinguished electrochemical performance, which can be applied in future flexible electronics.

Fiber-shaped supercapacitors are promising and attractive candidates as energy storage devices for flexible and wearable electric products. However, their low energy density (because their microstructure lacks homogeneity and they have few electroactive sites) restricts their development and application. In this study, well-distributed polyaniline/graphene composite fibers were successfully fabricated through a new strategy of self-assembly in solution combined with microfluidic techniques. The uniform assembly of polyaniline on graphene oxide sheets at the microscale in a water/N-methyl-2-pyrrolidone blended solvent was accompanied by the in situ reduction of graphene oxides to graphene nanosheets. The assembled fiber-shaped supercapacitors with gel-electrolyte exhibit excellent electrochemical performance, including a large specific areal capacitance of 541.2 mF cm⁻², along with a high energy density of 61.9 µW h cm⁻² at a power density of 294.1 µW cm⁻². Additionally, they can power an electronic device and blue LED lights for several minutes. The enhanced electrochemical performance obtained is mainly attributed to the homogeneous architecture designed, with an increased number of electroactive sites and a synergistic effect between polyaniline and graphene sheets. This research provides an avenue for the synthesis of fiber-shaped electrochemically active electrodes and may promote the development of future wearable electronics.