| Flexible supercapacitors（FSCs）with high specific energy(＞1 m W h cm–3)without compromising specific power have been a research focus in the field of energy storage/conversion.In this paper,a strategy has been developed for large scale synthesis of polypyrrole（PPy）films at the ice/liquid interface through a simple chemical oxidation method,yielding free-standing PPy films by melting the ice.The samples were characterized by X-ray diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,transmission electron microscopy,scanning probe microscopy,Raman spectroscopy,nanoindentation,and gel permeation chromatography.More significantly,symmetric planar flexible supercapacitors（FSCs）and rolled supercapacitors（RSCs）are fabricated by using individual PPy films as the active materials.The synthesis and electrochemical properties of PPy films were studied,the result as follows:（1）A strategy has been developed for large scale synthesis of polypyrrole（PPy）films,yielding free-standing PPy films by melting the ice.The molecular dynamics simulations evidence a monolayer deposition of pyrrole molecules on the ice surface through hydrogen bonding,supporting the formation of PPy films at the ice/liquid interface.This method can also be used for preparing other conductive polymer films.（2）By scanning electron microscopy,the thickness of PPy film increases with the increase of reaction time;Transmission electron microscopy showed that typical PPy nanofilm is a multilayer film;Fourier transform infrared spectroscopy showed that the conjugated length of PPy films increased with increasing reaction time to 6 h.Also,the conductivity of individual PPy films synthesized for 40 min exhibits the best conductivity.（3）The Cv values of FSCs from FSC-1 to FSC-5 at 3 m A cm–2are estimated to be5.16,3.83,2.57,2.07,and 0.62 F cm–3,with corresponding Ecell,v values of 0.72,0.53,0.36,0.29,and 0.09 mW h cm–3 in sequence.At a current density of 2 m A cm-2,the Ccell,v of RSC-1 is 16.8 F cm–3.（4）Typical FSCs and RSCs made from complete PPy films with film thickness of140±5 nm exhibit specific energy of 0.72 and 2.3 mW h cm–3 with corresponding specific power of 51.7 and 111.1 m W cm–3in sequence.After 5000 cycles at 2 mA cm–2,the ideal RSCs retain superior specific energy of 1.37 mW h cm–3,showing a great potential in practical applications.The synthesis and electrochemical properties of GN/PPy films were investigated,the results show that:（1）A strategy has been developed for large scale synthesis of GN/PPy films at the ice/liquid interface in-20°C,yielding free-standing GN/PPy films by melting the ice.（2）With increasing the mass ratio of graphene oxide/pyrrole,the conductivity increases first and then decreases.Raman spectra show that ID/IG increases first and then decreases with increasing the mass ratio of graphite oxide/pyrrole,which is consistent with the conductivity and capacitance properties of the samples.（3）The symmetrical flexible supercapacitor made from GN/PPy composite film,GN/PPy-3,exhibits a capacity of 190.5 mF cm-2 at a current density of 3 m A cm-2.After10,000 cycles,GN/PPy-3 symmetrical flexible supercapacitor exhibits a capacitance retention of 73.1%,showing a good cyclic stability. |
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