Ice-Templated Large-Scale Preparation of Two-Dimensional Sheets of Conjugated Polymers: Thickness-Independent Flexible Supercapacitance

Abstract

Two-dimensional (2D) organic materials hold great promise for use in a multitude of contemporary applications due to their outstanding chemical and physical properties. Herein, 2D sheets of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) are prepared from a commercially available PEDOT:PSS suspension using ice as a template. The 2D PEDOT:PSS sheets grow in the boundaries of ice crystals as the polymers are "squeezed" out of the suspension when the water solidifies. The mechanical robustness of the sheets can be enhanced by incorporating WO3 nanowires, and the PSS component can be conveniently removed with a concentrated solution of H2SO4 to afford stable suspensions of PEDOT or WO3@PEDOT sheets, either of which can be converted into flexible films with tunable thicknesses via filtration. Swagelok- or pouch-type supercapacitor devices prepared from the WO3@PEDOT films exhibit outstanding energy-storage characteristics, including high rate capability, thickness-independent energy storage (e.g., 701 mF cm(-2) is achieved with a 1-mm-thick film), high resistance toward mechanical deformation, and good cycling stability. Additionally, a high energy density of 0.083 mWh cm(-2) is measured for a device prepared using a 1-mm-thick film at a high power density of 10 mW cm(-2). The methodology described establishes an efficient and readily scalable approach for accessing 2D organic sheets.