Nickel current collector activated by ambient green laser for All-Printed microsupercapacitors

Abstract

Recently, a printable energy storage unit that can be integrated directly in planar circuit layouts has gathered tremendous attention for the realization of next-generation miniaturized electronics systems. Among various candidates, microsupercapacitors have been regarded as a viable one owing to their characteristic advantages of everlastingly long life-time, fast charge/discharge rate, and high frequency response. To date, patterned current collector features have been deposited by either evaporating extremely expensive gold metals or printing carbon-based composites with relatively low electrical conductance. In this study, we suggest air-ambient green laser activatable, cost-effective nickel current collectors that can resolve critical impediments of traditional noble metal and carbon-based current collectors. We synthesize, in air, 15-nm sized nickel nanoparticles with a localized surface plasmon characteristic in green wavelength, and formulate the printable paste comprising nickel nanoparticles and flakes (as metallic filler) and polyvinylpyrrolidone (as photoreactive reducing agent and carbonization source). Upon completion of green laser irradiation, the as-printed particulate layer is transformed into a highly conductive carbon-wrapped metallic skeleton with an electrical conductance of 54,300 S/m. Effectiveness as current collector is verified by stable operation of aqueous electrolyte and ionic liquid electrolyte-based microsupercapacitors in potential windows of 0.5 and 2.5 V, respectively, and electrochemical stability is also confirmed via XPS-assisted chronoamperometry analysis at a constant voltage of 4.25 V (vs. Li/Li+). We demonstrate that the laser activated, printed Ni current collector facilitates the fabrication of microsupercapacitors with an energy density of 77.3 mJ/cm(2) and a power density of 7.0 mW/cm(2), superior to the value obtainable in the gold current collector-based device.