Salt-concentrated acetate electrolytes for a high voltage aqueous Zn/ MnO2 battery

Shigang Chen, Rong Lan, John Humphreys, Shanwen Tao

    Research output: Contribution to journalArticlepeer-review

    34 Citations (Scopus)

    Abstract

    Aqueous rechargeable Zn/MnO 2 batteries are attractive due to their low-cost, high safety and use of non-toxic materials. In term of electrolyte materials, it is anticipated that an aqueous electrolyte with a wider electrochemical window will improve the stability and energy density. In this work, we investigated salt-concentrated electrolytes based on relatively inexpensive acetate salts. An electrochemical window of 3.4 ​V was achieved in salt-concentrated 1 ​m Zn(OAc) 2+31 ​m KOAc electrolyte. Its total ionic conductivity is 2.96 ​× ​10 -2 ​S ​cm -1 while the ionic conductivity of Zn 2+ ions is 7.80 ​× ​10 -3 ​S ​cm -1, estimated by a current interrupt method. This electrolyte is regarded as a mild alkaline environment with a pH value of 9.76, causing the different storage mechanism for anode with Zn 2+ ions and, cathode with OH - ions as the charge carriers respectively. A Zn/MnO 2 battery was assembled using 1 ​m Zn(OAc) 2+31 ​m KOAc electrolyte, self-supported α-MnO 2-TiN/TiO 2 cathode and Zn foil anode. The Zn/MnO 2 battery can be charged to 2.0 ​V versus Zn/Zn 2+ and delivers discharge capacity and energy density of 304.6 ​mAh·g -1 (calculated on the mass of MnO 2) or 0.32 mAh·cm -2 (calculated on the area of electrode) and, 368.5 ​Wh·kg -1 (calculated on the mass of MnO 2) or 232.7 Wh·kg -1 (calculated on the total active mass of electrodes and electrolyte) in the first cycle under a current density of 100 mA·g -1 (~ C/3, based on the mass of MnO 2) or 0.1 mA·cm -2 (based on the area of electrode). During cycling, the coulombic efficiency can be maintained around 99% and reached 99.9% during the 14-340th cycles. After the cycling tests, almost no dendrites were observed on the Zn foil anode attributing to the super-high salt concentration in that acetate-based electrolyte, which will benefit the stability of aqueous Zn/MnO 2 batteries.

    Original languageEnglish
    Pages (from-to)205-215
    Number of pages11
    JournalEnergy Storage Materials
    Volume28
    Early online date14 Mar 2020
    DOIs
    Publication statusPublished - Jun 2020

    Keywords

    • Aqueous rechargeable battery
    • Zn/MnO2
    • Acetates
    • Salt-concentrated electrolytes
    • WiBSE
    • Zn/MnO

    ASJC Scopus subject areas

    • Energy Engineering and Power Technology
    • Materials Science(all)
    • Renewable Energy, Sustainability and the Environment

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