Single and Double Layer of Monoclinic VO2 Ink Based Printed and Interdigitated Supercapacitors

Screen printing has received significant attention for manufacturing energy storage devices. However, preparing high-quality inks is still one of the main challenges. Herein, a homogenous and stable ink based on the monoclinic phase of VO2(M) microparticles has been synthesized by a simple hydrothermal process in only 6 h and through non-toxic solutions. The VO2 ink is printed on Kapton substrate in a single-layer as well as in a double-layer arrangement (1-LP and 2-LP). The printed 1-LP VO2 electrode delivers a maximum areal capacitance of 20 mF cm−2 with a small equivalent series resistance of 4 ohms without conducting additives. The interdigitated full-cell VO2 supercapacitor adequately employs the electric double-layer and Faradic redox mechanisms in 1.4 V, which is the highest operating voltage reported for symmetric supercapacitors based on pure vanadium oxide electrodes in aqueous inorganic electrolytes. Moreover, the maximum areal energy of the 2-LP supercapacitor is 0.8 µWh cm−2 at an areal power of 21.0 µW cm−2, which is larger than the 1-LP (0.2 µWh cm−2 at 17.5 µW cm−2). This improvement is attributed to the homogenously printed double-layer of the porous VO2 microparticles. Integrating such supercapacitors into thin-film electronics could develop portable devices.