Microfluidic-oriented assembly of MXene composite fibers for flexible zinc ion supercapacitors with high energy density

Abstract

Fiber-typed zinc ion hybrid supercapacitors (ZIHSCs) have become the potential electrode materials for new generation of energy storage devices due to its low cost, abundant source and its low redox potential can expand the operating voltage window and increase energy and power density. But, the development of ZIHSCs is still in its infancy, and it is necessary to optimize the structure of electrode materials and design fibrous devices. Two-dimensional MXene materials are widely used in electrode manufacturing, which is of great significance to the development of fiber-typed supercapacitors and is expected to become excellent cathode materials for zinc ion supercapacitors. However, assembling them into regularly arranged macrofibers is challenging. Here, we precisely regulated and constructed the ordered and porous reduced graphene oxides/MXene fibers (rGO/MXene) by microfluidic assisted wet spinning technology. Graphene oxide (GO) was used as a spinnable material and lamellar spacer to achieve 10 % rGO/MXene fiber with high MXene loading. Among them, 10 % rGO/MXene was used as a symmetric supercapacitor electrode material, and the specific capacitance in PVA/H₂SO₄ electrolyte was as high as 1613 mF cm⁻². The 10 % rGO/MXene fiber and 70 % rGO/MXene@Zn fiber were used as cathode and anode materials, and assembled into a zinc-ion hybrid supercapacitors (ZIHSCs) under PVA/Zn(CF₃SO₃)₂ gel electrolyte, and an outstanding specific areal capacitance of 1180 mF cm⁻², wide voltage window of 0–1.6 V, high energy density of 104.9 μWh cm⁻² and good practical applications can be realized. In addition, the capacitor has good stability at different bending angles. The expansion of energy and power output can be achieved by series or parallel configuration. This study provides a new way for the design of the high-performance flexible zinc ion supercapacitors.