Anodic Film Formation on Zinc in Alkaline Electrolytes Containing Silicate and Tetraborate Ions

Abstract

The reactivity of zinc in sodium hydroxide electrolytes containing sodium silicate and sodium tetraborate was studied by electrochemical and microstructural examinations. Impedance measurements indicate that a porous surface layer is formed on zinc immersed in sodium hydroxide at its open circuit potential and on polarization in the prepassive region. This surface layer becomes compact at potentials in the passive region. The anodic reactions of a zinc electrode in a sodium hydroxide containing electrolyte are controlled by the mass transport of zincate ions away from the electrode. Silicate and tetraborate ions suppress the anodic dissolution of zinc. In the presence of silicate ions, a compact silicate containing film is formed upon anodic polarization. The electrode rotation affects the microstructure of the surface layer both in silicate-free and silicate-containing sodium hydroxide solutions. On addition of tetraborate ions, the polarization resistance increases and the formation of a surface layer is achieved at increased applied potential.

Challenges, mitigation strategies and perspectives in development of zinc-electrode materials and fabrication for rechargeable zinc–air batteries

“…85 Great efforts have been made to investigate the origin of passivation in RZABs with focus on the electrolyte flow rate and the presence of specific ionic species in the electrolyte, particularly SiO 3 2À and Li + . 84,[86][87][88] For example,…”

“…Inorganic additives include metal salts, oxides and hydroxides, as well as organic salts. Various inorganic additives such as LiF, 124 KF, 124,138 88,127 have been employed to reduce the dendritic growth on the zinc-electrode. The introduction of the above additives into electrolytes usually leads to the formation of metal ions with a higher reduction potential than Zn.…”

“…Furthermore, the employment of ionic liquids for RZABs has also been proposed, which facilitates the suppression of self-corrosion of the zinc-electrode, slowing down the Reproduced with permission. 88 Copyright 2017, The Electrochemical Society. SEM images of Zn electrodeposition in the electrolyte adding (d) 0, (e) 10 À4 , (f) 10 À3 , and (g) 3 Â 10 À3 M SnO; and (h) charge increase vs. SnO content in anodic and cathodic scans.…”

Stripping Voltammetry for the Real Time Determination of Zinc Membrane Diffusion Coefficients in High pH: Towards Rapid Screening of Alkaline Battery Separators

“…All of these battery chemistries contain a Zn anode and a highly alkaline (pH>14) electrolyte. A main failure mechanism during cycling is poisoning of the cathode material due to “Zn crossover” . Upon discharging, Zn is readily solubilized as zincate (Zn(OH) 4 2− ) in the extremely basic electrolyte with concentrations reaching over 2 M .…”

“…A main failure mechanism during cycling is poisoning of the cathode material due to “Zn crossover” . Upon discharging, Zn is readily solubilized as zincate (Zn(OH) 4 2− ) in the extremely basic electrolyte with concentrations reaching over 2 M . The mobilized Zn(OH) 4 2− then diffuses across the separator and deposits as insulating ZnO or combines with other metal ions in the cathode (e. g. Mn ions) to form irreversible zinc‐metal oxides (such as ZnMn 2 O 4 ) thus limiting the cycle ability of the cathode and consequently the battery as a whole .…”