Influence of pressure and temperature on the electrolyte filling of lithium-ion cells: Experiment, model and method

Industrial filling of large lithium-ion cells with electrolyte liquid has a significant impact on the product quality and the production costs. This paper shows the influence of the process parameters, the pressure and the temperature, during dosing and wetting. A simple model based on a capillary is introduced and clarifies the relation between wetting and the process parameters. The model is compared to measurements of dosing and wetting experiments. The measurements were conducted using neutron radiography and electrochemical impedance spectroscopy. For industrial relevance, all experiments were carried out on PHEV1-cells with a capacity greater than 20 Ah. The results show a significant improvement in the wetting speed with elevated temperatures, low dosing pressure and moderate wetting pressure. The electrolyte reached all surfaces after 1.5 h for a refined choice of parameter combination. In contrast to a poor process design, where not even 40% of the area was wetted in the same time. This 2.5-fold wetting speed has significant advantages in terms of throughput and line utilization. The examined correlations lead to a methodical procedure for process design to overcome existing uncertainties in battery production.