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Harmonizing Energy and Power Density toward 2.7 V Asymmetric Aqueous Supercapacitor
Author(s) -
Xiong Ting,
Tan Teck Leong,
Lu Li,
Lee Wee Siang Vincent,
Xue Junmin
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201702630
Subject(s) - supercapacitor , overpotential , materials science , power density , capacitance , electrochemistry , chemical engineering , oxygen evolution , energy storage , aqueous solution , electrode , nanotechnology , power (physics) , thermodynamics , chemistry , physics , engineering
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, Na 0.25 MnO 2 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.