3D cellulose network confining MXene/MnO2 enables flexible wet spinning microfibers for high-performance fiber-shaped Zn-ion capacitors.

Fiber-shaped Zn-ion capacitors (FSZICs) have shown great potential in wearable electronics due to their long cycle life, high energy density, and good flexibility. Nevertheless, it is still a critical challenge to develop a conductive fiber with long size and high mechanical properties as the FSZIC cathode using sustainable and low-cost materials. Herein, regenerated cellulose (RC) -based conductive microfibers are prepared by a simple, continuous, and scalable wet spinning process. The 3D nanoporous networks of RC caused by physical self-cross-linking allow MXene and MnO2 to be uniformly and firmly embedded. The rapid extrusion and limited drying result in the highly aligned structure of the fibers, endowing the hybrid fiber with an ultra-high tensile strength (145.83 Mpa) and Young's modulus (1672.11 Mpa). MXene/MnO2-RC-based FSZIC demonstrates a high specific capacitance of 110.01 mF cm-3, an energy density of 22.0 mWh cm-3 at 0.57 A cm-3 and excellent cycling stability with 90.5 % capacity retention after 5000 cycles. This work would lead to a great potential of cellulose for application in next-generation green and wearable electronics.