Knittable energy storing fiber with high volumetric performance made from predominantly MXene nanosheets

A new member of the 2D family called "MXene" offers metallic conductivity and outstanding electrochemical properties that are important for developing fiber supercapacitors. To date, however, scalable approaches for preparing MXene-based fibres have been relatively unexplored. Here we demonstrate that a graphene oxide liquid crystal-assisted fiber spinning approach can be used to produce novel fibers that are predominantly MXene by weight (∼88 wt%). These MXene fibers exhibit high volumetric capacitance (∼341 F cm-3) and electrical conductivity (∼72.3 S cm-1) and excellent strength and flexibility that allow knitting of MXene-based textile prototypes. The supercapacitor device made from MXene fibers displays excellent stability after 20000 cycles and delivers maximum energy and power densities of ∼5.1 mW h cm-3 and ∼1700 mW cm-3, respectively. This work introduces a new class of fiber supercapacitors that offer great potential for realizing flexible power sources for miniaturized electronic gadgets and wearable technologies.