Electrochemical behavior of zinc particles with silica based coatings as anode material for zinc air batteries with improved discharge capacity

Titelangaben

Schmid, Manuela ; Willert-Porada, Monika:
Electrochemical behavior of zinc particles with silica based coatings as anode material for zinc air batteries with improved discharge capacity.
In: Journal of Power Sources. Bd. 351 (2017) . - S. 115-122.
ISSN 0378-7753
DOI: https://doi.org/10.1016/j.jpowsour.2017.03.096

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Abstract

Silica coatings on zinc particles as anode material for alkaline zinc air batteries are expected to reduce
early formation of irreversible ZnO passivation layers during discharge by controlling zinc dissolution
and precipitation of supersaturated zincates, Zn(OH)4
2-. Zinc particles were coated with SiO2 (thickness:
15 nm) by chemical solution deposition and with Zn2SiO4 (thickness: 20 nm) by chemical vapor deposition.
These coatings formed a Si(OH)4 gel in aqueous KOH and retarded hydrogen evolution by 40%. By
treatment in aqueous KOH and drying afterwards, the silica coatings were changed into ZnO-K2O$SiO2
layers. In this work, the electrochemical performance of such coated zinc particles is investigated by
different electrochemical methods in order to gain a deeper understanding of the mechanisms of the
coatings, which reduce zinc passivation. In particular, zinc utilization and changes in internal resistance
are investigated. Moreover, methods for determination of diffusion coefficients, charge carrier numbers
and activation energies for electrochemical oxidation are determined. SiO2-coated zinc particles show
improved discharge capacity (CVD-coated zinc: 69% zinc utilization, CSD-coated zinc: 62% zinc utilization)
as compared to as-received zinc (57% zinc utilization) at C/20 rate, by reducing supersaturation of
zincates. Additionally, KOH-modified SiO2-coated zinc particles enhance rechargeability after 100%
depth-of-discharge.