Reaction mechanisms for electrolytic manganese dioxide in rechargeable aqueous zinc-ion batteries.

Autor: Tran TNT; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada. tthuy@ualberta.ca.; Salient Energy Inc., Dartmouth, NS, B3B 1C4, Canada. tthuy@ualberta.ca., Jin S; Salient Energy Inc., Dartmouth, NS, B3B 1C4, Canada., Cuisinier M; Salient Energy Inc., Dartmouth, NS, B3B 1C4, Canada., Adams BD; Salient Energy Inc., Dartmouth, NS, B3B 1C4, Canada., Ivey DG; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada.
Jazyk: angličtina
Zdroj: Scientific reports [Sci Rep] 2021 Oct 21; Vol. 11 (1), pp. 20777. Date of Electronic Publication: 2021 Oct 21.
DOI: 10.1038/s41598-021-00148-2
Abstrakt: This study reports the phase transformation behaviour associated with electrolytic manganese dioxide (EMD) utilized as the positive electrode active material for aqueous zinc-ion batteries. Electrochemical techniques, including galvanostatic charge-discharge and rotating ring-disk electrode measurements, and microstructural techniques, using X-ray powder diffraction, scanning electron microscopy, and transmission/scanning transmission electron microscopy, were utilized to characterize the positive electrode at different stages of discharge and charge of zinc-ion cells. The results indicate that, during discharge, a fraction of EMD undergoes a transformation to ZnMn 2 O 4 (spinel-type) and Zn 2+ is intercalated into the tunnels of the γ- and ε-MnO 2 phases, forming Zn x MnO 2 (tunnel-type). When a critical concentration of Mn 3+ in the intercalated Zn x MnO 2 species is reached, a disproportionation/dissolution reaction is triggered leading to the formation of soluble Mn 2+ and hydroxide (OH - ) ions; the latter precipitates as zinc hydroxide sulfate (ZHS, Zn 4 (OH) 6 (SO 4 )·5H 2 O) by combination with the ZnSO 4 /H 2 O electrolyte. During charge, Zn 2+ is reversibly deintercalated from the intergrown tunneled phases (γ-/ε-Zn x MnO 2 ), Mn 2+ is redeposited as layered chalcophanite (ZnMn 3 O 7 ·3H 2 O), and ZHS is decomposed by protons (H + ) formed during the electrochemical deposition of chalcophanite.
(© 2021. The Author(s).)
Databáze: MEDLINE
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