Mechanically Stable Reduced Graphene Oxide/MXene Fibers with Exceptional Volumetric Capacitance and Energy Density Mediated by Carbon Nanotubes for High-Performance Symmetrical Supercapacitors

Flexible fiber-based supercapacitors (SCs) as power sources are highly anticipated for their potential applications in wearable and portable devices. However, it is still a big challenge to fabricate SCs with good electrochemical performance and high mechanical strength in a controllable and easy way. Here, we fabricated a reduced graphene oxide/Ti₃C₂T_x/carbon nanotube (rGO/Ti₃C₂T_x/CNT) fiber-based electrode using wet spinning and reduction processes. Benefiting from the π-π stacking interaction, hydrogen bonding and van der Waals’ forces between GO/Ti₃C₂T_x hybrid nanosheets and treated CNTs, a wearable, flexible, and knittable rGO/Ti₃C₂T_x/CNT-30 fiber electrode (272.0 MPa) was fabricated. More interestingly, the assembled symmetric all-solid SC from rGO/Ti₃C₂T_x/CNT-30 exhibited a high volumetric capacitance (C_v, 336.1 F·cm^-3) and an excellent cycling stability after 3000 cycles at a current density of 2 A·cm^-3. As a result, the fabricated SCs demonstrated a high volumetric energy density of 23.11 mWh·cm^-3 at a power density of 1600 mW·cm^-3 in the PVA/H₂SO₄ electrolyte. This work provides a designed rule for the fabrication of high-performance fiber-based SCs with potential applications in wearable, knittable, and portable devices.