Rheological and electrical properties of aqueous lithium iron phosphate suspension electrodes

Date

2024-1-26

Author

Yıldız, Bayram

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Developing homogeneous suspension electrodes characterized by low viscosity and high electrochemical performance is critical for the feasibility of suspension-based electrochemical energy storage technologies. One of the essential criteria for obtaining a homogeneous suspension is to use non-agglomerated particles. However, the use of agglomerated particles is unexpectedly common in most studies. This dissertation is focused on addressing the current gap in understanding the impact of the agglomeration characteristics of electroactive materials on the microstructure, flow, and electrical-electrochemical response of aqueous suspension electrodes and used lithium iron phosphate (LiFePO4, LFP) as a model system. First, a procedure was developed to synthesize individual LFP particles. The results highlighted the significance of post-synthesis processes not only on the agglomeration state of particles but also showed its influence on their electrochemical response. Second, the suspension formulation was optimized to obtain a homogeneous suspension electrodes capable of long-term stability. This optimization was a priori to acquiring stable and reproducible electrochemical impedance spectroscopy results. Third, the influence of the particles’ agglomeration state on the electrode characteristics was compared regarding its impact on suspensions’ microstructure, percolation characteristics, flow behavior, and electrical conductivity. This study showed that utilizing individual particles enabled an increase of 50% in the solids content in the suspensions while preserving their flowability and electrical conductivity. Lastly, fructose was used for the first time in an aqueous suspension electrode. Adding fructose noticeably enhanced the suspension electrode's discharge capacity and polarization. Although the underlying mechanisms of these improvements are yet to be studied, using the optimum amount of fructose increased the initial discharge capacity of LFP particles from 129 mAh/g to 151 mAh/g in an aqueous electrolyte.

Subject Keywords

Suspension Electrode, Agglomeration State, Flow-Assisted Energy Storage, Lithium Iron Phosphate, Suspension Microstructure

URI

https://hdl.handle.net/11511/108794

Collections

Graduate School of Natural and Applied Sciences, Thesis