Development and operation of an electrically rechargeable zinc-air flow battery

Abstract

Due to the limitations of present solutions, there is a demand for cost effective chemical energy storage for grid-scale applications. One promising example in development is the zinc-air flow battery, which could prove to be a key technology in ensuring energy security and the integration of renewable generation. Although the primary zinc-air chemistry is well studied and commercially available to progress the technology into a large-scale electrically rechargeable system requires significant development. Adapting the chemistry for suitability in large secondary systems has seen comparatively little attention and there are very few practical scale systems in operation. This thesis describes novel procedures for the fabrication of a gas diffusion electrodes suitable for use as a bifunctional oxygen electrode in alkaline secondary batteries. NiCo2O4 spinel catalyst was utilised as an alternative to precious metals in both carbon paper based and novel metal based gas diffusion electrodes. Air-electrodes were rapidly screened in a custom electrochemical lab scale half-cell. These electrodes were incorporated into a proof of concept zinc-air flow battery which could act as a preliminary design for future scale up. Electrodes up to 100 cm2 have be cycled for >24 hours operation at ≤50 mA cm-2. Balancing optimal operating conditions is presently a trade-off between many factors including durability/cycle life, electrochemical performance and electrode fabrication methods/cost. > 90% coulombic efficiently, > 60% voltage efficiency have been demonstrated with catalyst loadings of < 5 mg cm-2.

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ORCID for Richard Wills: orcid.org/0000-0002-4805-7589

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