The Role of Al3+-Based Aqueous Electrolytes in the Charge Storage Mechanism of MnOx Cathodes

24 November 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Rechargeable aqueous aluminium batteries are the subject of growing interest, but the charge storage mechanisms at manganese oxide-based cathodes remain poorly understood with as many mechanisms as studies. Here, we use an original in situ spectroelectrochemical methodology to unambiguously demonstrate that the reversible proton-coupled MnO2-to-Mn2+ conversion is the main charge storage mechanism occurring at MnO2 cathodes over a range of slightly acidic Al3+-based aqueous electrolytes. In Zn/MnO2 assemblies, this mechanism is associated with high gravimetric capacity and discharge potentials, up to 560 mAh·g-1 and 1.76 V respectively, attractive efficiencies (CE > 98.5 % and EE > 80%) and excellent cyclability (> 750 cycles at 10 A·g-1). Finally, we conducted a critical analysis of the data previously published on MnOx cathodes in Al3+-based aqueous electrolytes to conclude on a universal charge storage mechanism, i.e., the reversible electrodissolution/electrodeposition of MnO2.

Keywords

Aqueous Battery
MnO2
conversion process
Al-ion battery
Zn-ion
ITO coatings
Electrodeposition Process
proton uptake process
Rechargeable battery

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