Abstract
Corrosion and discharge behavior of battery-grade zinc particles coated with a silica layer doped with bismuth was investigated and compared with untreated zinc powder. Electrochemical investigations were carried out in half-cell configuration. The electrolyte was 6 M KOH in excess. Coated zinc particles provided a discharge capacity of 737 mAh g−1 (89.9% DoD) versus 633 mAh g−1 (77.2% DoD) of untreated zinc particles after a dwell time of 1 h in KOH. The silica coating reduced the direct contact of the zinc surface with the electrolyte and thus minimized the hydrogen evolution reaction, which led to an increased discharge capacity. Additionally, bismuth doping enhanced conductivity within the silica coating and increased zinc utilization. Those coated zinc particles inhibited corrosion, i.e., corrosion efficiency reached 87.9% compared to uncoated zinc. Additionally, the coating achieved a capacity retention of 90.9% (670 mAh g−1) after 48 h dwell time in 6 M KOH. The coatings were prepared by sol-gel technology and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface determination.
Highlights
Through the worldwide expansion of renewable energies, the development of energy storage technologies has become an essential part of research and development activities nowadays.In particular, electrochemical storage systems such as batteries are in focus
Battery-grade zinc for zinc-air battery anodes corrode in alkaline electrolyte during shelf life and discharge
In order to reduce corrosion, those zinc particles were coated with silica by a wet-chemical sol-gel process in order to prevent the direct contact of the zinc surface with the electrolyte
Summary
Electrochemical storage systems such as batteries are in focus Due to their long cycle life and high specific energy density, mainly Li-ion batteries are used today to store energy electrically. Among metal-air batteries, the zinc-air battery shows significant advantages such as high specific energy (1350 Wh kg−1 ), low costs, high availability of raw materials, good material recyclability, and safety [4,5,6,7,8,9] Despite these beneficial properties, zinc-air batteries are not preferred as rechargeable but as primary batteries, especially in hearing aids, due to their low cycle life [4,10,11].
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