Harmonizing Energy and Power Density toward 2.7 V Asymmetric Aqueous Supercapacitor. Issue 14 (26th January 2018)

• Record Type: Journal Article
• Authors: Xiong, Ting; Tan, Teck Leong; Lu, Li; Lee, Wee Siang Vincent; Xue, Junmin
• Is Part Of: Advanced energy materials. Volume 8:Issue 14(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-01-26
• Subjects: electrochemical reduction -- high energy densities -- high power densities -- Na+ insertion -- wide potential windows; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201702630
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: Tremendous research efforts are devoted to developing wide potential window aqueous supercapacitors to resolve their low energy density concern. While the operational potential window is dictated by the intrinsic electrochemical stability of water (1.23 V), such a bottleneck may be surpassed by leveraging the additional overpotential of the oxygen evolution reaction and the hydrogen evolution reaction (HER). Herein, by employing an electroreduction technique, Na + is adsorbed onto the carbon negative electrode which effectively acts as a physical barrier to hinder intermediate HER product formation, thereby reducing HER activity. To complement the wide potential carbon electrode, Na0.25 MnO2 is employed as the positive electrode to take advantage of the extra energy (i.e., increased overpotential) required for Na + insertion process into the structure. The asymmetric supercapacitor exhibits high energy density of 61.1 W h kg −1 at a power density of 982 W kg −1, and even at an ultrahigh power density of 42.9 kW kg −1, a respectable energy density of 16.3 W h kg −1 is attained. In addition, 93.7% capacitance retention is recorded after cycling for 10 000 cycles which further demonstrates its suitability as supercapacitor. The present success in fabricating a 2.7 V asymmetric supercapacitor will open a promising research route toward achieving high energy density and high power density. Abstract : Controlling hydrogen evolution reaction and oxygen evolution reaction activities is a key strategy toward widening the operating potential window of aqueous supercapacitor. As such, a simple electrochemical technique is employed in this work to prepare the wide potential window negative and positive electrodes. Herein, a 2.7 V asymmetric supercapacitor with high energy density and high power density is achieved.