Free-standing electrochemically coated MoSx based 3D-printed nanocarbon electrode for solid-state supercapacitor application

The 3D-printing technology offers an innovative approach to develop energy storage devices because of
its ability to create facile and low cost customized electrodes for modern electronics. Among the recently
explored 2D nanomaterials beyond graphene, molybdenum sulfide (MoS_x) has been found as a promising
material for electrochemical energy storage devices. In this study, a nanocarbon-based conductive
filament was 3D-printed and then activated by solvent treatment, followed by electrodeposition of MoS_x
on the printed nanocarbon electrode’s surface. The conductive nanocarbon fibers allow a coaxial deposition
of a thin MoS_x layer. The MoS_x layer contributes to pseudocapacitive charge storage mechanisms to
obtain higher capacitances. In a three-electrode test system with 1 M H₂SO₄ as electrolyte, the MoS_x
coated 3D-printed electrode (MoS_x@3D-PE) electrode shows a capacitance of 27 mF cm⁻² at the scan
rate of 10 mV s⁻¹, and a capacitance of 11.6 mF cm⁻² at the current density of 0.13 mA cm⁻². Extending
to solid-state supercapacitor (SS-SC), the cells were fabricated using the MoS_x@3D-PE with different
designs and polyvinyl alcohol (PVA)/H₂SO₄ as gel electrolyte. An interdigital-shaped SS-SC provided a
specific capacitance of 4.15 mF cm⁻² at a current density of 0.05 mA cm⁻². Moreover, it showed a stable
cycle life where 10% capacitance loss was found after 10000 cycles. Briefly, this study reports the integration
of 3D-printing and room-temperature electrodeposition techniques allowing a simple way of fabricating
customized free-standing 3D-electrodes for use in SC applications.