Furthering the Resurgence of Zinc Batteries in the Age of Rechargeability Through Scalable Anode Material Synthesis
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Wilson, Evan Nathaniel
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Abstract
Herein, two separate zinc anode projects are combined into one work. The overarching theme of this work is the focus on zinc anodes and the constraint of affordable precursor materials and scalable material processing with the goal of achieving commercializable performance.
The first project is a carbon-coated \ce{ZnO} anode material for use in Ni-Zn alkaline rechargeable batteries. To achieve the desired morphology and functionality of the carbon coating, a two step process with spray drying and annealing was selected as the synthesis approach after reviewing the literature on scalable production of core-shell battery materials. The precursors selected for the carbon coating and zinc oxide were thermoset water-based polymer and zinc oxide nanoparticles, based on a review of the literature as well as the constraints inherent to the spray drying and annealing synthesis approach. Two candidate carbon precursors were attempted, however both had problems when used to make an ion-sieving carbon coating for zinc anodes. The first carbon precursor, polyurethane, had a poor coating quality with a pore structure that was too open, with wide pores allowing dissolved zinc species to escape, and with a poor electrical contact to the contained zinc oxide, resulting in poor zinc utilization. The second carbon precursor, resol, catalyzed hydrogen evolution, resulting in inefficient battery charging as well as self-discharge and mechanical degredation of the anode, all of which led to rapid capacity loss upon full-cell cycling. A different carbon precursor is needed to enable this technology, perhaps with a change in materials processing associated with the constraints of future promising carbon precursor materials.
The second project is a porous 3D host material for zinc anodes, which includes an alloy-seeding approach which uses a thermodynamic advantage to direct the nucleation of zinc and maintain electrode structure over long-term cycling. The material was successfully synthesized and early testing showed much promise in the reversibility of the anode material, however the full-cell platform of neutral zinc-air with fluoridated electrolyte is relatively new and the available commercial air electrodes were not designed for either the presence of zinc ions in solution at high concentration or the high current density which the alloy-seeding 3D zinc host is capable of cycling with, and so the performance of the full cell was artificially limited, calling for more research in the future with a better cathode pairing.
While both projects were not successful in achieving their performance goals, both technologies may yet be successful with additional research due to the sound nature of their underlying concepts.
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Date
2022-01-18
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