The most cost‐intensive components of the battery system for electric vehicles are the lithium‐ion battery cells. Thus, to reduce the overall cost of a battery system, a clear objective is to reduce the production cost of lithium‐ion battery cells. Cost drivers are to be identified, which are essential to enable potentials for cost reduction. In particular, the formation and aging process represents a high potential for process cost reduction because of its enormous process time expenditure. The automotive industry requires up to 3 weeks for the formation and aging process of a single lithium‐ion battery cell. Due to the high relevance of these processes, the research project OptiZellForm as part of the ProZell Cluster examines those production steps in detail. Environmental conditions such as mechanical load and elevated temperature as well as the electrical and chemical properties influencing the formation and aging process are investigated. The focus of this study is the investigation of the mechanical exertion and elevated temperature with regard to the reduction of the formation process duration and thus the reduction of the production cost. For this reason, a specially designed device is used to investigate these parameters for lithium‐ion battery cells.

The increasing relevance of automotive lithium‐ion battery cells spotlights the importance of economic production in a high quantity. In this context, production technology for large battery formats is of great relevance. Therefore, it is necessary to identify effects on important cell properties, and based on this, develop an understanding of the interaction between process parameters and product properties. Large‐format cells are not comprehensively examined, particularly, in a large sample size, analyzing cell properties in terms of distributed values. Hence, there is so far no statistical data concerning large‐format batteries and their distributed discharge capacity and self‐discharge. For this reason, and in contrast to other studies, the scope of this work is to investigate a large sample size of 79 industrial‐scale 9 Ah battery cells to ensure statistical relevance and generate distributed data of cell properties. For this purpose, a large number of cells are produced and extensively electrochemically investigated. Subsequently, the essential parameters are correlated with the electrode parameter of carbon black particle size. Hence, the foundation for this process–product–property relationship is laid.

Lithium-ion batteries are a key technology for electromobility; thus, quality control in cell production is a central aspect for the success of electric vehicles. The detection of defects and poor insulation behavior of the separator is essential for high-quality batteries. Optical quality control methods in cell production are unable to detect small but still relevant defects in the separator layer, e.g., pinholes or particle contaminations. This gap can be closed by executing high-potential testing to analyze the insulation performance of the electrically insulating separator layer in a pouch cell. Here, we present an experimental study to identify different separator defects on dry cell stacks on the basis of electric voltage stress and mechanical pressure. In addition, finite element modeling (FEM) is used to generate physical insights into the partial discharge by examining the defect structures and the corresponding electric fields, including topographical electrode roughness, impurity particles, and voids in the separator. The test results show that hard discharges are associated with significant separator defects. Based on the study, a voltage of 350 to 450 V and a pressure of 0.3 to 0.6 N/mm2 are identified as optimum ranges for the test methodology, resulting in failure detection rates of up to 85%.

Laser cutting is a promising technology for the singulation of conventional and advanced electrodes for lithium-ion batteries. Even though the continuous development of laser sources, beam guiding, and handling systems enable industrial relevant high cycle times, there are still uncertainties regarding the influence of, for this process, typical cutting edge characteristics on the electrochemical performance. To investigate this issue, conventional anodes and cathodes were cut by a pulsed fiber laser with a central emission wavelength of 1059–1065 nm and a pulse duration of 240 ns. Based on investigations considering the pulse repetition frequency, cutting speed, and line energy, a cell setup of anodes and cathodes with different cutting edge characteristics were selected. The experiments on 9 Ah pouch cells demonstrated that the cutting edge of the cathode had a greater impact on the electrochemical performance than the cutting edge of the anode. Furthermore, the results pointed out that on the cathode side, the contamination through metal spatters, generated by the laser current collector interaction, had the largest impact on the electrochemical performance.

The cell characterization in the incoming inspection is an important but time and cost intensive process step. In order to obtain reliable parameters to evaluate and classify the cells, it is essential to design the test procedures in such a way that the parameters derived from the data allow the required statements about the cells. Before the focus is placed on the evaluation of cell properties, it is therefore necessary to design the test procedures appropriately. In the scope of the investigations two differently designed incoming inspection routines were carried out on 230 commercial lithium-ion battery cells (LIBs) with the aim of deriving recommendations for optimal test procedures. The derived parameters of the test strategies were compared and statistically evaluated. Subsequently, key figures for the classification were identified. As a conclusion, the capacity was confirmed as an already known important parameter and the average cell voltage was identified as a possibility to replace the usually used internal resistance. With regard to capacity, the integration of CV steps in the discharging processes enables the determination independently from the C-rate. For the average voltage cycles with high C-rates are particularly meaningful because of the significant higher scattering due to the overvoltage parts.