TY - JOUR
T1 - Origin of capacitance decay for a flower-like δ-MnO2 aqueous supercapacitor electrode
T2 - The quantitative surface and electrochemical analysis
AU - Justin Raj, C.
AU - Manikandan, Ramu
AU - Sivakumar, Periyasamy
AU - Opar, David O.
AU - Dennyson Savariraj, A.
AU - Cho, Won Je
AU - Jung, Hyun
AU - Kim, Byung Chul
N1 - Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/2/5
Y1 - 2022/2/5
N2 - Herein, we report the electrochemical energy storage performance of δ-MnO2 (K-birnessite MnO2) as supercapacitor electrode material in Na2SO4 aqueous electrolyte. The electrode exhibited considerable electrochemical performances due to the fast intercalation/deintercalation reactions of Na+ on the pseudocapacitive MnO2 surface. However, a long-term cyclic stability test of the electrode at a low specific current (1 A g−1) demonstrated a decline in its initial capacitance value to the tune of ~ 21%. To quantify the above discrepancy, the electrochemical intercalation of Na+ ions on the electrode surface was quantitatively studied employing electrochemical impedance spectroscopy, EDAX analysis and X-ray photoelectron spectroscopy. Further, the surface of the electrode was analyzed by performing complete charge and charge/discharge measurements at a low specific current of 0.1 A g−1. These results disclosed that, besides the surface intercalation/deintercalation reactions, some Na+ ions have permanently substituted into the bulk (layer) of δ-MnO2 by replacing the host K ions from the layered nanostructure. Thus, this finding suggests that Na+ ions replaced in the site of K in δ-MnO2 considerably affect the electrochemical properties of the supercapacitor electrode.
AB - Herein, we report the electrochemical energy storage performance of δ-MnO2 (K-birnessite MnO2) as supercapacitor electrode material in Na2SO4 aqueous electrolyte. The electrode exhibited considerable electrochemical performances due to the fast intercalation/deintercalation reactions of Na+ on the pseudocapacitive MnO2 surface. However, a long-term cyclic stability test of the electrode at a low specific current (1 A g−1) demonstrated a decline in its initial capacitance value to the tune of ~ 21%. To quantify the above discrepancy, the electrochemical intercalation of Na+ ions on the electrode surface was quantitatively studied employing electrochemical impedance spectroscopy, EDAX analysis and X-ray photoelectron spectroscopy. Further, the surface of the electrode was analyzed by performing complete charge and charge/discharge measurements at a low specific current of 0.1 A g−1. These results disclosed that, besides the surface intercalation/deintercalation reactions, some Na+ ions have permanently substituted into the bulk (layer) of δ-MnO2 by replacing the host K ions from the layered nanostructure. Thus, this finding suggests that Na+ ions replaced in the site of K in δ-MnO2 considerably affect the electrochemical properties of the supercapacitor electrode.
KW - Impedance spectroscopy
KW - Ion intercalation
KW - Layered nanostructure
KW - Manganese oxide
KW - Supercapacitor
UR - http://www.scopus.com/inward/record.url?scp=85116501693&partnerID=8YFLogxK
U2 - 10.1016/j.jallcom.2021.162199
DO - 10.1016/j.jallcom.2021.162199
M3 - Article
AN - SCOPUS:85116501693
SN - 0925-8388
VL - 892
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
M1 - 162199
ER -