Examination on Battery Technology for Scale-up of a Lithium Ion Battery

To develop battery technology for a large-sized lithium ion battery, particle size of electrode active material, compression of electrodes, drying conditions of electrodes, and electrolyte identities were examined using a coin-cell, and the treatment of the lower edge of electrodes, electrode size, adhesion of electrode active material and current collector, and impregnation condition of electrolytes, were studied using single cells. The followings are particularly important findings obtained in this study. (1) Residual pyrrolidone caused an increase in water content, and thus, drying of electrodes is important in large-sized batteries. (2) Adhesion of electrode active material and current collector can be improved by either increasing the thickness of the current collector or by using an accurate-sized frame during the compression step of electrodes. (3) Both sides of the lower edge of the electrode were covered by precipitates of the Li dendrite during charge-discharge of the battery, and this precipitation was greatly inhibited by applying paste consisting of 75% natural graphite and 25% PVdF at the edge of the anode. (4) Impregnation of electrolytes to large-sized batteries is very difficult compared to that in small ones, since the uniform contact between electrolytes and electrodes requires a longer time. (5) Sealing of the battery case using a viton o-ring can efficiently avoid the mixing of water inside the battery and the evaporation of solvent outside the battery.