Boosting the Energy Density of Carbon‐Based Aqueous Supercapacitors by Optimizing the Surface Charge

Abstract

The voltage of carbon-based aqueous supercapacitors is limited by the water splitting reaction occurring in one electrode, generally resulting in the promising but unused potential range of the other electrode. Exploiting this unused potential range provides the possibility for further boosting their energy density. An efficient surface charge control strategy was developed to remarkably enhance the energy density of multiscale porous carbon (MSPC) based aqueous symmetric supercapacitors (SSCs) by controllably tuning the operating potential range of MSPC electrodes. The operating voltage of the SSCs with neutral electrolyte was significantly expanded from 1.4 V to 1.8 V after simple adjustment, enabling the energy density of the optimized SSCs reached twice as much as the original. Such a facile strategy was also demonstrated for the aqueous SSCs with acidic and alkaline electrolytes, and is believed to bring insight in the design of aqueous supercapacitors.

Designing Carbon Based Supercapacitors with High Energy Density: A Summary of Recent Progress

“…The optimized porous carbon with pore sizes centered at 4 nm was fabricated by using polyvinylpyrrolidone precursor, showing a specific capacitance of 118 F g −1 in 0.5 m H 2 SO 4 at 5 mV s −1 . Most Recently, Yu et al . reported a spraying‐pyrolysis method to obtain multi‐scale porous carbon, based on a polyvinyl alcohol/NiCl 2 /KOH hydrogel (Figure ).…”

“…Reproduced with permission from reference Reproduced with permission from Ref. Copyright 2017, WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.…”

“…For example, Cheng's group demonstrated a novel charge injection strategy to modify the surface charge state of carbon electrode in electrolyte of LiPF 6 /EC/DMC. As revealed by the result, this method could negatively shift P 0V , significantly enhancing the operating voltage (3.0 V to 4.3 V) and energy density (≈10‐fold enhancement) Recently, Yu et al . proposed a novel pre‐charging strategy to effectively adjust the operating potential window, motivated by full utilization of the promising potential range.…”

Aqueous supercapacitors based on carbonized silk electrodes

“…The reason why the voltage window of SC-850-based symmetric supercapacitors can reach 2.0 V is because this carbon material has a great development of hydrogen evolution or hydrogen oxygen overpotential. 28,[64][65][66] The conventional symmetric supercapacitors based on SC-850 electrodes were assembled with an additional reference electrode monitoring the respective potential variation of the anode and cathode when the assembled SC-850-based symmetric supercapacitors were charged/discharged at 1 A g À1 with a voltage of 2.0 V (Fig. 6d: the upper limit of oxygen evolution potential, PU; the lower limit of hydrogen evolution potential, PL).…”

Electrochemical Double‐Layer Capacitor Energized by Adding an Ambipolar Organic Redox Radical into the Electrolyte

“…[23,24] Recently,d ifferent redox mediators have been reported, such as halogen ions, [25,26] Cu/Cu 2+ , [27] Fe 2+ / Fe 3+ , [28,29] and hydroquinone/quinone. [31][32][33][34] Hence,researchers turned to introduce dual redox mediators for two electrodes,r espectively. [31][32][33][34] Hence,researchers turned to introduce dual redox mediators for two electrodes,r espectively.…”