Effect of Electrode Fabrication Process on the Crystallinity of PVDF Binder and Electrochemical Performance of Electrode

Abstract

In lithium ion battery in fabrication of electrode with good mechanical performance, active materials and conductive agent have to be mixed with specific polymer as binder to binding the other components together. As an effective binder, the polymer should meet some requirements for battery performance and production, such as excellent adhesion to current collector, suitable cohesion to active material and conductive agent, good electrochemical stability over a wide voltage window, high lithium ion conductivity, and so on. Because the binder may coat on the surface of active material particles, the binder layer should have high ionic conductivity and lithium ion can pass through the binder. Poly (vinylidene fluoride) (PVDF) is the mostly common used binder in lithium ion battery production. The amorphous phase in PVdF is a good matrix for polar molecules, and lithium ions can pass through a thin layer of swollen PVdF[1]. PVDF is a semi-crystalline polymer with a repeating unit of –CH2-CF2-. The spatial arrangement of the CH2 and CF2 groups along the polymer chains can contribute to the unique properties of PVDF from its crystalline phase. But it is seldom researched that the effect of crystalline structure of PVDF on the electrochemical performance in lithium ion battery. In our recent study, we found that the impedance of electrode is dependent on the drying temperature of coated slurry[2]. In this research we investigated the relationship of process conditions with crystalline phases of PVDF binder in the electrode and the dependence of the electrochemical performance of the electrode on the process conditions.[1]. K. Tsunemi , H. Ohno , E. Tsuchida , Electrochimica Acta , 28 (6) , 591 (1983) .[2]. Y. Fu, X. Song, G. Liu, V. Battaglia, 236th ECS Meeting ,353, Oct. 13-17, 2019, Atlanta, GA. Figure 1