Spherical LiMn₂O₄ fine powders with two different morphologies were prepared by ultrasonic spray pyrolysis. SEM and TEM observation showed that the type of starting solution influenced particle morphology. The particle structure derived from nitrate precursor solution was porous, while the powders derived from acetate precursor solution consisted mainly of hollow particles. XRD revealed that as-prepared powders were well crystallized into spinel structure with Fd3m space group. Atomic absorption spectrometer analysis showed that the chemical composition of LiMn₂O₄ was in agreement with that of the starting solution. The first charge/discharge capacity of LiMn₂O₄ obtained from metal nitrate and acetate was 120-130mAh/g. The discharge capacity of LiMn₂O₄ decreased with increasing cycle number. The cycle performance of LiMn₂O₄ obtained from metal nitrate was superior to that of LiMn₂O₄ obtained from metal acetate. It was found that the cycle performance was influenced by the morphology and microstructure of LiMn₂O₄ particles.

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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.

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Composite process by the deposition of fine particles onto surfaces of core particles with a new vessel type mixer has been analyzed. In this paper, a new apparatus based on a high-speed elliptical-rotor-type mixer is proposed. The effects of rotor revolution and processing time on the composite process were investigated, and the composite particles for fuel cell electrodes such as MCFC and SOFC were fabricated. As a result, the mass fraction of fine particles strongly fixed on the core particle surface increased with the rotor revolution and the processing time below the critical revolution. Adding small portion of fine particles repeatedly to the powder was effective to achieve a higher mass fraction of fine particles on the core particle surface.
Filament-shaped Ni particles were successfully covered with fine CoO particles, and NiO sphere particles were also uniformly covered with fine YSZ particles by making use of the apparatus.

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We observed serious reduction of SOFC performance due to the agglomeration of Ni particles and the shrinkage of anode made by powder mixture of fine NiO and YSZ particles. Therefore, a new microstructure of anode, which is referred to as “YSZ-supported anodes”, has been proposed in order to overcome the aforementioned problem of the anode. The uniqueness of the new anode is such that YSZ powders are divided into two coarse and fine fractions. It was found that dimension, porosity and electrical conductivity of these anodes were more stable than that of the previous one, and that slight changes in the cell voltage were observed under a constant current flow of 0.4A/cm². The present investigation of anodes suggests that the two YSZ particles form a solid framework and prevent damage due to Ni agglomeration.

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