Shearing MXene Sediment Enables Formation of the Liquid Crystal Phase for Spinning Ultradense Fibers with High Electrochemical Performance

Construction of a dense microstructure with closely packed MXene nanosheets is vital for realizing high-capacitance fibers. Starting with MXene sediment, which is a dense suspension consisting of a large number of unexfoliated MXene nanosheets, this work reveals that long-time shearing enables an ordered arrangement of MXene nanosheets into a liquid crystal phase. Wet spinning of sheared MXene sediment results in the direct formation of ultradense fibers without the need to tune the chemical composition of the coagulation solution. This approach is additive-free and also controllable since the microstructure of fibers is highly associated with shearing time. The results show that 36 h of shearing yields a fiber with a high density of 5.39 g cm–3. This fiber is highly conductive and also shows an exceptionally high electrochemical performance including a volumetric specific capacitance of ∼1661 F cm–3 in 1 M H2SO4 electrolyte, a volumetric specific capacitance of ∼875 F cm–3 in a semisolid electrolyte, and a capacity retention rate of 93% after 500 cycles. The supercapacitor exhibits an excellent energy density of 105.7 mWh cm–3 and a power density of 500 mW cm–3.