黏結劑之物理形態對鋰離子電池正極生胚組成均勻性的影響研究

高分子黏結劑為鋰離子正極材料的重要組成之一，其在電極內的相對含量與分佈均勻性會影響電池的電化學性質表現。然而，由電極材料所配製之電極漿料在極板乾燥過程中，黏結劑因溶劑揮發而產生的遷移現象與黏結劑含量有關，進而影響電極生胚的分散均勻性及生胚與鋁基板間的黏附強度，導致電池性能產生差異。當黏結劑添加濃度較高時，黏結劑於電極內部的遷移行為較不顯著，電極材料分佈均勻性相對較佳並有利於電化學性質的表現；然而電極的內部阻抗卻會因為絕緣性之高分子黏結劑含量的提高而變大。反之，當黏結劑於電極中含量較低時，不但電極材料於極板內部的組成分佈將會較為不均勻，且極板生胚與鋁基板間的黏附強度亦會下降而造成生胚於充放電過程中脫落。另一方面，黏結劑的物理形態可分為乳膠型(Latex)及溶解型(Dissolution) ，兩者對於粉體的吸附機制截然不同，因此黏結劑之物理形態亦會對其遷移現象產生影響。基於上述中黏結劑之添加濃度、物理形態和在極板中之遷移行為對電極品質的影響性，本研究即探討添加不同物理形態之黏結劑與磷酸鋰鐵(LiFePO4)正極材料分散均勻性之間的關係。

關鍵字

磷酸鋰鐵；黏結劑；分散；遷移率；電化學

並列摘要

Organic polymer binder is one of essential ingredients in cathodes of lithium-ion batteries, which both its concentration and distribution homogeneity in cathodes have been found exhibiting great impact on the electrochemical performances of batteries. In this research, it was found that organic binders are not uniformly distributed in the electrode sheets because they migrate with solvent during the drying process of electrodes, and the amount of being migrated showed closely related to the added concentration. The migration results would affect the adhesion properties of cathode materials on the current collector and the eventual cell performance. Based on the experimental data, we also found that the migration of organic binder is less significant when its content in the cathode is higher; that is, the binder is more uniformly distributed and the electrochemistry is better for the cathodes with higher content of binder. However, having higher content of insulated organic binder is not always beneficial because it may increase the inner electrical resistances of cathodes, on the other hand, and lead to poor electrochemical properties. Besides, less content of binder causes non-uniformity of its distribution in cathodes and decreases the adhesion of cathode materials on the current collector, and sometimes the cathode sheet may even exfoliate from the collector during the battery charging and discharging. Hence, having an appropriate addition of binder in cathodes is important and a necessity. On the other hand, the physical morphologies of organic polymer binders, such as latex- and dissolution-typed binders, were found to have different adsorption mechanisms on the cathode active powders. The different adsorption behaviors altered their migrations with solvent. Therefore, the effects of physical morphology of binders on the distribution homogeneity of cathode materials and the resulted cell performance were also discussed in this thesis.

並列關鍵字

LiFePO4 ； Binder ； Dispersion ； Migration ； Electrochemistry

參考文獻

[1] Y.S. Meng, M.E. Arroyo-de Dompablo, “Recent Advances in First Principles Computational Research of Cathode Materials for Lithium-Ion Batteries,” Acc. Chem. Res., 46, 2013, 1171.

[2] H. Gao, L. Jiao, J. Yang, Z. Qi, Y . Wang, H. Yuana, “High rate capability of Co-doped LiFePO4/C,” Electrochim. Acta, 97, 2013, 143.

[3] C.C. Li, X.W. Peng, J.T . Lee, F .M. Wang, “Using Poly(4-Styrene Sulfonic Acid) to Improve the Dispersion Homogeneity of Aqueous-Processed LiFePO4

Cathodes,” J. Electrochem. Soc., 157, 2010, 517.

[4] A. Kristoffersson, E. Roncari, C. Galassi, “Comparison of Different Binders for Water-based Tape Casting of Alumina,” J. Eur. Ceram. Soc., 18, 1998,

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黏結劑之物理形態對鋰離子電池正極生胚組成均勻性的影響研究

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