In Situ Synthesis of ZIF-67 Thin Films Using Low Temperature Chemical Vapor Deposition to Fabricate All-Solid-State Flexible Interdigital in-Planar Microsupercapacitors

Abstract

This work describes the fabrication of a flexible all-solid-state interdigital in-planar microsupercapacitor (μSC) using the in situ synthesized ZIF-67 thin films as the interdigital finger-electrode materials, platinum (Pt) thin film as the interdigital finger-electrode current collector, laser print technology for the fabrication of interdigital patterns, and low-cost commercial polyethylene terephthalate (PET) sheet as the flexible substrates, assembled with the NaOH/PVA gel electrolyte. ZIF-67 thin films are in situ synthesized onto PET substrate by ultralow temperature (ULT) chemical vapor deposition (CVD) technology at a low temperature of 140°C. We herein report the ULT CVD approach for gas phase synthesizing ZIF-67 thin films, the exactly heating temperature can produce vaporized water steam, sublimated 2-methylimidazole (2-MIM) and cobalt(II) acetylacetonate (Co(acac)2) vapors at the same time. The vaporized and sublimated gaseous precursors demonstrated molecular-level reactions, including the deprotonation of 2-MIM via water steam, and the following coordinated reactions with cobalt ions decomposed from Co(acac)2, for the efficiently straightforward deposition to form the uniform ZIF-67 thin films onto the substrate surface. Herein, the integration of pattern printing, CVD depositing ZIF-67 thin films, and lift-off patterning processes demonstrated a comprehensive achievement and good compatibility to integrate MOFs into miniaturized energy-storage devices.