UTILIZATION OF COLLOIDAL PRINCIPLES IN CARBON COATING OF ELECTROACTIVE MATERIALS

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2022-9-1

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Aşkar, Yasemin

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The increasing energy demand requires battery systems with high volumetric energy density, therefore one of the current aims is to maximize the amount of active material that can be loaded per unit volume. This situation is directly related to the particle agglomeration state and dispersible particles are required to achieve high volumetric energy density. Carbon coating, which is used to increase the electrical conductivity of active materials, also plays a significant role in the agglomeration of the particles. For this reason, in this thesis, it was aimed to develop a suitable carbon coating procedure in such a way that individual electroactive materials maintain their dispersibility. Herein, as a novel approach, colloidal principles and a proceeding pyrolysis step were used to synthesize dispersible particles with full carbon coverage. LiFePO4 (LFP) electroactive material was chosen as the model system. Individually dispersible LFP particles were produced with the polyol method. After zeta potential analyses on pristine LFP particles, CTAB (cetyltrimethylammonium bromide) was chosen as the surfactant and used as a carbon source for pyrolysis. The critical ratio of CTAB to LFP at which zeta potential reverses sign and stabilizes were determined and a two-stage pyrolysis procedure was designed. The optimal carbon-coated individual particles produced in this process and bare LFP were compared in terms of their dispersibility, tap density, and electrochemical performance. The tap density of the pristine LFP (1.11 g∙cm-3) and carbon-coated LFP particles (1.16 g∙cm-3) was obtained quite similar. Results demonstrate the applicability of the zeta potential analysis-based approach utilized herein producing homogeneous carbon coating without any loses in tap density and dispersibility.

Subject Keywords

Carbon Coating, Colloidal Stabilization, Dispersible Electroactive Material Synthesis, Lithium Iron Phosphate, Cetyltrimethylammonium Bromide

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https://hdl.handle.net/11511/99636

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

Y. Aşkar, “UTILIZATION OF COLLOIDAL PRINCIPLES IN CARBON COATING OF ELECTROACTIVE MATERIALS,” M.S. - Master of Science, Middle East Technical University, 2022.