Analysis of Mechanical Properties of Composite Electrode with Different Binder Molecular Weights

Abstract

In order to improve the energy density of the lithium ion battery, the loading level of the electrode is continuously increasing. As a result, the presence of inactive materials such as conductive materials / binders in the electrodes is also highlighted. In particular, securing the mechanical properties of the electrode according to the distribution and composition of the binder is becoming more important in terms of long-term reliability. However, increasing the composition of the binder of the electrode can ensure the mechanical properties of the electrode at the same loading level and density, but increases the resistance of the electrode. This increase in resistance may reduce the lifetime of the electrode, apart from the mechanical properties of the electrode. Therefore, in order to minimize the resistance increase rate of the electrode and to secure mechanical properties, the mechanical properties and resistance of the electrode according to the molecular weight of the binder in the electrode were analyzed.In this presentation, three LiCoO2 electrodes with different PVDF binder molecular weights of 500,000 / 630,000 / 1,000,000 were prepared, and the adhesion and volume resistivity of the electrodes were measured using SAICAS and Electrode Resistance Meter. Although the adhesion of the electrodes was different according to the molecular weight of the PVdF binder, the increase in the volume resistivity of the electrode was not large. This is because the behavior of the binder and the active material / conductive material in the electrode are different from each other as the molecular weight of the binder increases, and the mechanical properties of the binder are also different according to the molecular weight. In order to confirm this more intuitively, the battery was fabricated and the behavior of the electrode was observed. Furthermore, the physical properties of the polymer were analyzed according to the molecular weight of the binder in order to clarify the cause.