Effects of compositional homogeneity on the cell performance of LiCoO2 cathodes

• Main Authors: Ya-Hui Wang, 王雅慧
• Other Authors: Chia-Chen Li
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/pa595k

碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 100 === The fabrication of Li-ion battery has been discussed by wet mixing process is this investigation. Dispersion property and drying conditions will change the homogeneity of the resulted cathode sheets to affect the physical and electrochemical properties. This investigation studied effects of binder compositions on the homogeneity and electrochemical performances, in which the binder used including the aqueous-based composited of SBR & SCMC and the organic-based PVDF. It has been known that binder plays an important role in the powder dispersion system. When binder can be to adsorbed on the surface of particles, steric hindrance will be generated between particles, and the slurry will reveals a very stable condition. Cathode sheets manufactured by the well dispersed slurries can exhibit better electrochemical performances. The electrochemical properties of cathode sheets with containing composite different ratios of SBR and SCMC were discussed in this investigation. Where cathode particles are adsorbed by the binder molecules, the steric hindrance in cathode slurries due to the adsorptions may have them being cell stabilized. It was fond that the binder that is free and not adsorbed on powder could migrate with solvent up to evaporation the surface of the cathode tape during drying, resulting in an inhomogeneous distribution of binder content in the dried electrode sheet. When binder shows larger migration, the adhesion force between particles will decrease, and so does the adhesions between the cathode sheet and the aluminum foil could become poorer, and so does the electrochemical performance. Based on the theoretical calculations, it can be understand that the non-uniform distribution of binder in the cathode sheet are dominated by the migration control theory mechanism. The dispersion homogeneity of cathode slurries were practical examined in the measurements of zeta potential and rheology. The physical & electrochemical properties of the dried cathode sheets were assessed on the measurements of adhesion force, electrical resistance, AC-Impedance and rate capabilities.