Rheology Engineering for Dry-Spinning Robust N-Doped MXene Sediment Fibers toward Efficient Charge Storage.

MXene nanosheets are believed to be an ideal candidate for fabricating fiber supercapacitors (FSCs) due to their metallic conductivity and superior volumetric capacitance, while challenges remain in continuously collecting bare MXene fibers (MFs) via the commonly used wet-spinning technique due to the intercalation of water molecules and a weak interaction between Ti 3 C 2 T X nanosheets in aqueous coagulation bath that ultimately leads to a loosely packed structure. To address this issue, for the first time, a dry-spinning strategy is proposed by engineering the rheological behavior of Ti 3 C 2 T X sediment and extruding the highly viscose stock directly through a spinneret followed by a solvent evaperation induced solidification. The dry-spun Ti 3 C 2 T X fibers show an optimal conductivity of 2295 S cm -1 , a tensile strength of 64 MPa and a specific capacitance of 948 F cm -3 . Nitrogen (N) doping further improves the capacitance of MFs to 1302 F cm -3 without compromising their mechanical and electrical properties. Moreover, the FSC based on N-doped MFs exhibits a high volumetric capacitance of 293 F cm -3 , good stability over 10 000 cycles, excellent flexibility upon bending-unbending, superior energy/power densities and anti-self-discharging property. The excellent electrochemical and mechanical properties endow the dry-spun MFs great potential for future applications in wearable electronics.