| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 102 === It has been understood the interaction between binders, conductive agents and other cathode materials makes impacts on the dispersibility of electrode slurry. In this research, the thickener of sodium carboxymethyl cellulose (SCMC) and the binder of
Styrene Butadience Rubber (SBR) were used as a complex binder to investigate the gelation mechanism of the same type but different lots of commercialized lithium iron phosphate (LFP) cathode material in water-based slurry.
Carbon coating technique has been widely used to overcome the drawback of intrinsic poor electronic conductivity of typical commercialized LFP cathode materials. However, once LFP particle surface is not covered by evenly distributed carbon coating, the exposed LFP particle surface will have higher polarity, as compared with uniformly carbon coated cases. The polarized LFP surface forms hydroxyl groups easily because of chemical absorption reaction. The hydroxyl groups attached on the surfaces of LFP and SCMC bond together to form intermolecular hydrogen bonding which leads to the formation of a 3-dimentional structure, causing the phenomenon of slurry gelation.
The discrepancy of surface characteristics between different lots of LFP powder were analyzed by Zeta potential, Fourier transform infrared spectroscopy(FTIR) and
Raman spectroscopy. The impacts of dissolution mechanism on the dispersibility of water-based slurry were studied by measuring the tendency of zeta potential.
Moreover, the differences of chemical compositions of several lots of LFP powder, e.g. the content of lithium phosphate on the surface of powder, were analyzed via X-ray photoelectron spectroscopy (XPS). Finally, the impact of lithium phosphate residues on powder surface on the gelation mechanism of water-based LFP was confirmed via rheological behavior measurement.
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