High Al-ion storage of vine shoots-derived activated carbon: New concept for affordable and sustainable supercapacitors

New era heteroatom-doped carbons, relying on different biomass residues, play a rising role in contemporary carbon energy storage technology. Herein, an abundant waste of viticulture industry – vine shoots (VS) was carbonized and examined as electrode material for supercapacitors with non-conventional aqueous electrolyte. Biochar obtained by pre-carbonization treatment of vine shoots (at 300 °C) is impregnated with ZnCl2 at 600 °C (ACvs600) and 700 °C (ACvs700), to synthesize carbon with developed specific surface area, close to 1500 m2 g−1. The high specific capacitance of ACvs is achieved in Al-based electrolyte, which allows working voltage of 1.8 V ACvs700/Al2(SO4)3/ACvs700 cell delivers the energy density of 24 Wh kg−1 at 1 A g−1, which is higher than one measured in typical Na2SO4 (∼16 Wh kg−1) and H2SO4 electrolyte (∼11 Wh kg−1). By using Trasatti&Dunn surface charge distribution models, the reallocation of inner vs. outer charge in Al-based electrolyte is found to be different from that in H2SO4 electrolyte. The nature of the interaction between pristine/defective graphene and hydrated Al3+ ion is examined by Density Functional Theory (DFT) and discussed. Gathered experimental and theoretical data open novel perspectives for using carbon in more sustainable energy storage devices.