A phenylenediamine-mediated organic electrolyte for high performance graphene-hydrogel based supercapacitors

Abstract

We prepare a novel redox-additive organic electrolyte containing phenylenediamine for a graphene-hydrogel supercapacitor. By adopting this electrolyte, significant capacity enhancement (47–596% increase) is achieved. At the concentration of 0.02 mol l−1, the specific capacity value of the graphene-hydrogel electrode reaches 171 mAh g−1, 287 mAh g−1, and 353 mAh g−1 at 1 A g−1 for o-phenylenediamine (OPD), m-phenylenediamine (MPD), and p-phenylenediamine (PPD), respectively. The enhancement by PPD is more significant than OPD and MPD at concentrations higher than 0.02 mol l−1. This behavior is likely caused by the para-amino groups, which exhibits less stereo-hindrance during the absorption of phenylenediamine onto the graphene surface. In the electrolyte containing 0.04 mol l−1 of PPD, specific capacity of 516 mAh g−1 at 1 A g−1 and energy density of 143 Wh kg−1 with power density of 1.11 kW kg−1 are achieved. Meanwhile, 93.8% of the electrode's initial capacity (433 mAh g−1) is retained after 5000 cycles at 2 A g−1, demonstrating its excellent cycling stability.