Energy-Dense Aqueous Carbon/Carbon Supercapacitor with a Wide Voltage Window

Abstract

Amplification of energy density with zero compromise on power density is a major challenge in capacitive science. Since energy density has a quadratic dependence on voltage, broadening the operating voltage window of the supercapacitors (SCs) could be an effective strategy to boost the energy density over improving the electrode’s capacitance if one can avoid excessive leakage current density. On extending the voltage window of the SC beyond the water electrolysis potentials in an aqueous medium, the combined effect of the choice of the electrode material and pH of the electrolyte plays an important role. In the present work, activated carbon (ACTS-800) derived from Tamarind seeds, a widely available cheap bio-mass, pyrolyzed at 800 °C, is explored as a potential electrode material for fabricating a high voltage SC in aqueous 1 M Na2SO4. Interestingly, the beneficial interaction between the surface functional groups and electrolyte resulted in the high overpotentials for both hydrogen and oxygen evolution reactions in the neutral medium. ACTS-800 exhibited superior performance in terms of energy density (28 Wh kg−1), and leakage current density (0.33 mA cm−2) to many reported carbon materials derived from various bio-sources.

RETRACTED: Capacitive Behavior of Aqueous Electrical Double Layer Based on Dipole Dimer Water Model

“…Although aqueous electrolytes have disadvantages such as narrow electrochemical windows of 1.23 V due to the hydrogen/oxygen evolution reactions, they have benefits of high ionic conductivity, non-flammability, and low manufacture costs in comparison with their organic counterparts. In fact, the limitation of the narrow electrochemical window can be overcome in highly concentrated aqueous electrolytes, also known as water-in-salt (WiS) electrolytes [ 8 , 9 , 10 , 11 , 12 , 13 ], which have been shown to significantly widen the electrochemical stability window to over 3.0 V, via interface modification [ 14 , 15 ], or the development of chemically stable, high surface area carbon structures [ 16 , 17 , 18 ]. As a result, aqueous electrolytes are still popular in the study of EDLCs [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ].…”

Battery-like supercapacitive behavior of urchin-shaped NiCo2O4 and comparison with NiCo2X4 (X = S, Se, Te)

“…possess the above-mentioned properties and are acceptable as EDLCs electrode materials. 14,15 Pseudocapacitive electrode materials should have variable oxidation states for the fast reversible redox reactions to happen. Considering this fact, metal oxides, hydroxides, carbides, nitrides, conducting polymers, etc.…”

Ultrahigh-voltage aqueous electrolyte for wide-temperature supercapacitors

“…3a-e 3f †). These results further indicated that a high voltage stability and high coulombic efficiency of AC-based SC with 1 M Na 2 SO 4 /H 2 O/EG electrolyte can be simultaneously obtained, which is a much better performance than that of other reported aqueous electrolytes 11,13,15,[18][19][20][21] (Table 1).…”