Impact of Li-Ion slurry formulation on cathode defects caused by calendering process

Summary:

In the current work, the influence of the cathode formulation on the physical and mechanical properties after calendering and slitting was studied. A mixture design method was exploited to evaluate the impact of different components in the final electrode. Mixture design is a statistical analysis based method, which allow one to gain quite extensive information about the studied system with minimized practical experiments. The investigated cathode in the current work consisted of NMC622, carbon black, SFG-6L and PVDF. The electrodes were designed as high-energy cathode with an active mass loading of 30 mg cm-2 each side. The electrode density after calendering was 3 g cm-3. A range of formulations was prepared in the lab-scale. The relative resistance as well as the bending behavior (also called camber effect) of the electrode after calendering were measured and analyzed. The camber of the cathode was quantified after calendering by using a precised ruler. The apparent electronic resistivity was measure by an in-house developed experimental set-up. The results showed that lowering the PVDF content while increasing the additives content in the formulation at the same time could reduce the camber effect of the cathode. In addition, with this strategy the apparent electronic conductivity of the high-energy cathode can also be improved. Utilizing both responses (camber and resistance) with respect to the electrode components from the laboratory experiments, a predicted profile from regression analysis could be proposed. An optimal range of component compositions can be defined where the two response requirements are met. To verify the proposed model, two or more formulations need to be carried out in the pilot line, which will be presented in the future work.