Variation of the MnO2 Birnessite Structure upon Charge/Discharge in an Electrochemical Supercapacitor Electrode in Aqueous Na2SO4 Electrolyte

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• 作者：Laurence Athou&euml ; l ; Franç ; ois Moser ; Romain Dugas ; Olivier Crosnier ; Daniel Bé ; langer ; Thierry Brousse
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：May 8, 2008
• 年：2008
• 卷：112
• 期：18
• 页码：7270 - 7277
• 全文大小：226K
• 年卷期：v.112,no.18(May 8, 2008)
• ISSN：1932-7455

文摘

This paper provides new insight on the charge storage mechanism in crystallized Mg-doped sodium birnessite-type manganese dioxide used as active supercapacitor electrode material that involves the intercalation/deintercalation of cations between the sheets during electrochemical reduction/oxidation, respectively. Anincrease of the interlayer spacing from 0.710 to 0.720 nm upon electrochemical oxidation in the presence ofNa⁺ cations in the electrolyte is associated with the deintercalation of Na⁺ and the intercalation of H₂Obetween the layers. A progressive crystallinity loss of the material is also observed upon potential cyclingbetween the oxidized and reduced states. Despite these structural changes, the birnessite electrode exhibits astable capacitance of 145 F/g over 1100 cycles.