Keijiro Terashita

Kneading and dispersion of positive electrode materials in a lithium ion secondary battery for high-density film

Focusing on the manufacturing process of the positive electrode of the lithium ion secondary battery, this research set out to investigate the kneading and dispersion that is required to distribute positive electrode particles of a high density within the film, and to investigate methods for evaluating the state of dispersion of the positive electrodes. We demonstrated that the dispersion of the positive electrode particles of the lithium ion secondary battery can be quantitatively evaluated by measuring the particle size distribution of positive electrode particles in the paste, the volume resistivity of the film, the film thickness, the film density and the glossiness, and by organically analyzing these measured values. Moreover, we revealed that, in order to manufacture high-density film, it is better to adopt the method of adding the binder in divided stages. In other words, we pointed out that in order to make positive electrode particles fill the film (plate) of a high density and to create good battery characteristics, the kneading and dispersion processes are extremely important. Furthermore, we were able to obtain a good correlation between volume resistivity and film density. In short, to produce a film that excels in battery properties, it is essential to increase the film density.

Moisture feedback control and process automation in fluidized bed granulation

A new practical method for self-control of the fluidized bed granulation process will be described. The method consists of moisture feedback control and program control of each operation (i.e. mixing, granulation and drying). An IR moisture sensor which is resistant to powders and dusts has been designed and developed to continuously measure and control the granule moisture content in fluidized bed granulation. The effect of the moisture content, imbibition rate and time required for fixed command control on granule growth is discussed, and a model of agglomeration and the mechanism of granule growth is proposed. On the basis of the results obtained granule growth was fully controlled by means of the moisture feedback control and, in addition, automation of the fluidized bed granulation process was eventually established.

Recent work in Japan on the mixing of solids

Abstract During the last ten years, about sixty papers dealing with solids mixing, segregation, sampling and simulation have been published in the academic journals in Japan. This review surveys the literature related to the motion and flow characteristics of solid particles, the power consumption of mixers, continuous mixing, and simulation of the mixing processes.

Preparation of electric conductive particles by dry coating.

Preparation of composite conductive particles was attempted by coating fine electric conductive powders on insulative core particles so called dry coating. Compressive crushing mill was utilized for the dry coating process. Polymethylmethacrylate (PMMA, 8μm in diameter) was used as core particles. TiO2 coated with Ag (0.5μm in diameter), TiO2 coated with SnO2 (0.2μm) and SnO2 particles (less than 0.1μm) were employed as fine electric conductive powders. In the experiments, the rotation speed of the mill and the treatment time were changed. The coating condition and electric conductivity of the prepared particles were determined by volume specific resistivity, SEM observation of the particle surfaces and the compression moldings of the particles and X-ray micro-analysis.As a result, composite particles with the functions of charge prevention and electromagnetic shield were procured by the dry coating process. In the conductive compression moldings, electric conductive routes were formed by the contacts of fine electric conductive particles and aggregates, coated or dispersed on the core particles. A network of good electric conductive routes was obtained when primary particles of the conductive powder were dispersed uniformly. It was obvious that the excellent conductive composite particles (coated with the fine electric conductive powder) were obtained when the particles were acted by shearing force and compression force.

Dispersion of Carbon Black in Resin by Kneading with a Continuous Kneader and the Evaluation of the Dispersion

A keading experiment was carried out on thermoplastic resin and carbon black (materials for toner) with a continuous kneader using the kneading temperature as a variabe. In addition to measuring the mixing torque in kneading and the residence time of the material, evaluation of the condtion of dispersion was attempted by means of image analysis.The results showed that image analysis enables the assessment of the condition of carbon black dispersion in the kneaded material. It also shows, that the degree of dispersion in the kneaded material both radially and axially increases depending on the material in which the mixing action works as well as with increases in the kneading energy.

Tensile strength and internal friction factor of wet fine coal.

The tensile strength and other parameters of wet fine coal with various water contents were determined by tensile breakup and direct shearing tests, in which the period of aging after increasing the water content was also varied. On the basiss of the results obtained, the flowability of wet fine coal was evaluated.The tensile strength of wet fine coal in the pendular to funicular states increased with an increase of water content. However, in a mixture of funicular and capillary states the tensile strength either stayed almost constant or decreased after reaching a maximum value. The flowability of wet fine coal (wet powders) may be better evaluated by the tensile strength and shearing force rather than the internal friction factor. This implies that the higher the tensile strength and shearing force increase, the more the flowability is reduced. Furthermore, the prolongation of the aging period improves the flowability of wet fine coal, because the tensile strength is reduced by penetration of water into the coal particles.

Internal Friction Factors of Powder by Constant Volume Shear Test

A new type of constant volume shear tester has been developed to obtain the yied loci by a single experimental run. By utilizing this tester, the shear stress which is converted in to the internal friction factor was measured for the several kinds of powders.The tester was attatched with the sensors detecting the normal stress distribution (6points) above and below the shearing plane.The internal friction factor obtained using constant volume shear tester was compared with that by a constant vertical stress tester.The findings are as follows:(1) Whether the type of tester is constant volume of constant vertical stress does not affect the normal stress distribution, but it depends on the sorts of powder.(2) The shearing stress τx measured by the constant volume tester agrees with the peak shearing stress τx, max observed by tha vertical constant stress tester for coarse powders. For fine powders, the τx coincides with the steady state shearing streess provided by the constant stress tester.(3) Both types of the testers make significant difference in the internal friction factors calculated by the normal stress acting on the shear plane.