Abstract
Production of positive electrodes for superior lithium ion secondary battery depends basically on the formation of high-density film of positive electrode materials on a metal plate. The present work studied the dispersion of positive electrode materials by changing operating conditions of kneading and dispersion, and the methods for evaluating dispersion of positive electrode materials were discussed. First, positive electrode materials were kneaded and dispersed into pastes. The coated film was prepared on an aluminum plate by spreading the pastes. Second, the dispersion of electrode materials was evaluated in terms of volume resistance, density and gloss of the coated film. Last, the particle size distributions of pastes were measured and the relationships between properties of the coated film were examined. It was reconfirmed that the dispersion of positive electrode materials for lithium ion secondary battery can be quantitatively evaluated from the measured values, such as particle size distribution of pastes, volume resistance, thickness, density and gloss of the coated film.
The experiments showed that continual addition of small amounts of thickener was preferred to prepare the densely packed coated film. It was also confirmed that positive electrode materials are packed densely by intensive dispersion even if the coated film is thin, and that the coated film for lithium ion secondary battery with a superior electric conductivity is prepared by adding small amount of a thickener continually. This result showed that kneading and dispersion influenced remarkably the packed density of the coated film and characteristics of batteries.
