Synthesis and electrochemical performance of high entropy oxides as an anode for lithium-ion batteries

Date

2023-12

Author

Bayraktar, Deniz Okan

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Lithium-ion batteries are indispensable part of our lives. Ever since their commercial applications the demand for higher performance is ever increasing. Increase in performance can be achieved by ingenious cell designs but the better performing active materials allows a bigger leap in the electrochemical performance. That is why industry and academia is in a perpetual race to achieve better performing products. One of such highly researched materials is high entropy oxides (HEO). High entropy oxides are demonstrating interesting properties both in terms of electrochemical and physical characteristics. One of the main objectives of this work is to investigate the lithium-ion diffusion properties and electrochemical properties dependance on the structure of the high entropy oxide material. For this reason, the effects of the synthesis environment of flowing argon and air on the structural and electrochemical properties of powders of (FeMnCrCoZn)3O4 high entropy oxides are investigated in this study. HEO synthesized in argon atmosphere (HEO-Ar) and the one synthesized in air (HEO-Air) were structurally and morphologically characterized. The increased electrochemical performance of HEO-Ar compared to HEO-Air has been shown. The oxygen vacancies, characterized by x-ray photoelectron spectroscopy method, in the HEO-Ar sample improve electrochemical performances by increasing the number of sites for Li+ accommodation, increasing conductivity, and accelerating Li+ diffusion kinetics. Both materials, although, having higher specific capacities, demonstrate higher operating voltages compared to graphite. Knowing these properties gives both material designer and cell designer the ability to design materials and electrochemical cells according to the specific application of energy storage. Considering their enhanced current rate capabilities and extended cycle life these materials may possibly be used in grid level applications, such as peak shaving, grid support and renewable energy storage.

Subject Keywords

Lithium-ion batteries, High entropy oxides, Anode

URI

https://hdl.handle.net/11511/107571

Collections

Graduate School of Natural and Applied Sciences, Thesis