Date of Award

Fall 2023

Document Type

Open Access Dissertation

Department

Chemical Engineering

First Advisor

William Mustain

Abstract

Primary zinc alkaline batteries power a wide array of everyday use electronic devices such as remote controls, calculators, cameras, and flashlights and will own an appreciable share of the battery market for the foreseeable future. Primary alkaline batteries generally utilize carbon, gas diffusion air, or manganese dioxide cathode but always coupled with a slurry zinc anode. There are several issues with this primary alkaline platform, largely emphasized by the performance of the zinc anode, such as a gassing phenomenon which leads to battery rupture and under certain circumstances, low material utilization leading to low energy density. The gassing and material utilization issues are attributed to corrosion and passivation, respectively, which are two well understood processes in the field of electrochemistry, material science, and corrosion. Through an industrial collaboration between Dr. Mustain and Duracell, I played a large role in eking out a statistically driven understanding of corrosion and material utilization dynamics of the zinc slurry anode including things like zinc particle size, shape, and crystallinity, surfactant type and concentration, zinc powder loading, and KOW wt.% in the electrolyte. All these factors were shown to influence the zinc slurry performance (corrosion propensity and achievable capacity) and an understanding of the interaction of these factors on the performance of the anode was made possible by my largest contribution to the field – the repurposing of an EQCM cell for studying zinc slurry in 3-electrode. Historically, zinc anode electrochemistry in 3-electrode on zinc foils and slabs: both of which are non-porous planar structures. Zinc slurries are immensely more complicated than the simple electrode geometry inferred by foils and slabs and are preferred as real systems use zinc slurries and not low surface area foils or slabs. Additionally, other components are included in the zinc slurry anode such as electrode additives such as gellants and surfactants which complicate the understanding of its electrochemical performance. Developed and discussed in-depth first in this work is a recrystallization process we developed in which polycrystalline zinc powder is recrystallized such that the grain sizes are approximately doubled and many of the smaller particles are single crystal. We then go on to demonstrate that the recrystallized zinc powder performs better in both corrosion and achievable capacity measurements. Tafel analysis and constant current discharge experiments confirm that recrystallized zinc powder performs better than the industrially as-received polycrystalline predecessor. Following demonstration of a scalable method to recrystallize zinc powder, we then go on to systematically study a 64 powder-type cohort of zinc powders based on particle size, shape, and crystallinity, using our custom built 3-electrode ex-situ platform, allowing us to rapidly screen the powders and slurries. The powders and slurries were probed for corrosion propensity via linear sweep voltammetry and linear polarization resistance and were studied for achievable capacity via constant current discharge. It was shown and is discussed at length which particle features contribute the most and least to reducing corrosion and boosting achievable capacity. Following the statistical powder and slurry analysis based on particle features, we then turned our attention to studying the influence of organic additives, surfactants, on the performance of the zinc slurry. It was observed and shown through various types of interestingly designed and executed experiments with our 3-electrode platform that different surfactant additives have different behaviors in electrolyte. Some surfactants can bind to and directly influence the electroactive surface while others have less of a binding propensity and more of an influence on activities of ions in the electrolyte space. These surfactant behaviors were probed and demonstrated with our 3-electrode platform. We went on to use the platform to screen different zinc slurry formulas containing different surfactant types, surfactant loadings, zinc powder weight percents, and KOH weight percents in the electrolyte. All the information gleaned from our ex-situ data collection and subsequent statistical analysis led to an improved in-situ performance. This work demonstrates the power of our 3-electrode platform in driving an understanding of what is happening inside of the complex milieu of zinc slurries. Further, this work demonstrates the power of an intelligently designed DOE and the robustness of our 3-electrode platform to rapidly screen hundreds of samples of zinc slurry and powder in a very reasonable amount of time, by one person.

Rights

© 2024, Brian James Lenhart

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