Pencil drawn paper based supercapacitors

Abstract

This is the first comprehensive analysis of paper-based supercapacitors, P-SCs, that are produced utilising commercially available pencils to draw an interdigitated design upon common household printing paper, developing cheap, green and reliable low profile electrical conductors and electrodes. The P-SCs are optimised in terms of the composition of pencil used, the number of layers and the analysis of single or double sided interdigitated electrode designs; such a comprehensive study is seldom explored in previous literature. A full analysis of the physical and electrochemical properties of the pencil drawn electrodes has been performed, including the application of a new capacitive testing/evaluation circuit applied to charge/discharge measurements/analysis, which provides a revolutionary and unambiguous analysis of the capacitance of the fabricated electrodes; an easy to use experiment guide is presented. The P-SCs are benchmarked using 0.1 M H₂SO₄ as the aqueous electrolyte. The P-SCs demonstrate a specific capacitance of ∼10.6 μF mg⁻¹ at a charge current of 0.46 A g⁻¹. The P-SCs are integrated into a novel pouch design, providing a flexible, cheap and easily manufactured supercapacitor, which demonstrates a capacitance of ∼101.4 μF, exhibiting a specific capacitance of ∼42.4 μF g⁻¹ at a current density of 0.46 A g⁻¹, exhibiting energy and power densities of ∼0.45 J mg⁻¹ (0.125 mW h mg⁻¹) and ∼0.03 W mg⁻¹ respectively. The pouch cell, fabricated from P-SCs, utilises five parallel double-sided pencil drawn electrodes, with paper separators, and retains 82.2% of its maximum capacitance, after 5121 charge/discharge cycles at a current density of 0.09 A g⁻¹. Last, a solid state P-SC is developed utilising a PVA–H₂SO₄ solid electrolyte, which demonstrates a specific capacitance of 141.8 μF g⁻¹, at a charging current of 4.33 μA g⁻¹.