Influence of the electrolyte quantity on lithium-ion cells

In the production process chain of lithium-ion battery cells, the filling process is eminent for the final product quality and costs. The filling consists of several dosing steps of electrolyte liquid into the cell and the subsequent (intermediate) wetting of the cell components. The quantity of electrolyte filled not only has an impact on the wetting rate of electrodes and separator but also limits the capacity of the cell and influences the battery lifetime. However, too much electrolyte is dead weight, results in a lower energy density and unnecessarily increases the costs of the battery. To ensure low costs in production and at the same time high quality of the cells, the optimal amount of electrolyte is studied in this paper. Based on experimental data from electrochemical impedance spectroscopy, the filling process, the formation process as well as a lifetime test, the interdependencies between electrolyte quantity, wetting rate, capacity, energy density and lifetime are presented for large-format cells.