| 초록 |
In rechargeable lithium ion batteries, composite electrodes consisting of active material, conducting material, and binding material have been used for both practical use and fundamental researches. In order to obtain precise electrochemical and physicochemical parameters, composite electrodes are not suitable because of electrochemical potential and reaction distributions in porous electrode. One of promising solutions is usage of thin film electrode, but it is not real material. In this study, electrochemical measurements were performed by using micrometer size single particle to eliminate effects from electrolyte solution side and porous nature. Both diffusion coefficient of Li+ and charge transfer resistance were determined from this single particle measurement for LiCoO2 and graphite particles which size were 10 ~ 30 ㎛. The obtained electrochemical parameters indicate that these active materials have enough high diffusion coefficients to realize 100 C rate discharge with 90 % discharge capacity of theoretical one. On the other hand, the charge transfer resistances were a little bit high to obtain fast discharge and charge cycles at 100 C. In conclusion, the charge transfer resistance should be reduced by modifying an interface between active material and electrolyte including surface film formation or enlarging surface area of active materials. |
