Flexible Supercapacitors Utilising the Multifunctional Rôle of Ionic Liquids

The method consisted of an in situ polymerisation of pyrrole in a solution of cellulose in the ionic liquid, 1-butyl-3-methylimidazolium chloride. The resulting polypyrrole-cellulose composite film was chemically blended, and it showed flexible polymer properties while retaining the electronic properties of the polypyrrole. Addition of a hydrophobic ionic liquid, trihexyl(tetradecyl)phosphonium bis{(trifluoromethyl) sulfonyl}amide and graphite powder enhanced the flexibility and conductivity of the composite films, respectively.<br><br>The composites films obtained were applied as electrodes in flexible supercapacitors using a simple scalable method to design flexible, ultrathin and safe supercapacitors.

Three devices were fabricated, (i) electrical double-layer supercapacitors, (ii) electrochemical supercapacitors and (iii) hybrid supercapacitors. The multifunctional rôle of ionic liquids as solvent, electrolyte and plasticiser was exploited to fabricate these novel flexible supercapacitors which showed an excellent cycle life of 15000 cycles with nearly 100 % of capacitance retention, an operational voltage between 1.6 V and 3.2 V and a maximum energy and power density of 0.008 μW h cm-2 and 1.78 μW cm-2, respectively.

Moreover, the design nature of these electrodes, chemical stability and feasibility to use biocompatible components will enable the fabrication of task-specific flexible supercapacitors with durable cycle life and chemical stability.