rGO-CMC fiber supercapacitors with core-sheath structure manufactured by coaxial extrusion printing

Fiber-shaped supercapacitors are attractive as an energy storage unit due to their excellent flexibility. However, fabricating robust fibers with large yields remains a challenge. In this work, we prepare flexible core-sheath fibers via coaxial extrusion printing. Carboxymethylcellulose sodium salt (CMC) slurry with controlled rheological properties is extruded from the outer channel, while the graphene oxide (GO) slurry is extruded from the inner channel simultaneously. The followed freeze-drying process protects GO sheets from agglomeration, providing more efficient chemical reduction. The reduced GO (rGO) sheets are separated and expanded to fill in the CMC sheath, which eliminates the delamination between the CMC sheath and rGO core. We study the influences of the freeze-drying process on the fiber microstructures, and explore the slurry design, fiber quality, reduction condition, and electrochemical performance. The fabrication method allows scalable manufacturing of the core-sheath electrodes and fiber-shaped supercapacitors with more efficient conductive networks.