This work is an overview of various equivalent circuits (ECs) containing various degrees of detail. The ECs are evaluated in terms of model accuracy and parameterization time for the systematic assignment of an equivalent circuit to application fields. For this purpose, impedance spectra were measured using electrochemical impedance spectroscopy at different states of charge, health and temperatures. Then the parameters of the EC were extracted using the least‐squares method and the Levenberg–Marquardt algorithm. After comparing the simulated to the measured impedance spectrum, a review and assignment of equivalent circuits for potential applications is given. Simple equivalent circuits with a series resistor and a maximum of two resistance–capacitance (RC) elements are ideal for simulations with lower dynamics. Equivalent circuits with up to five RC elements or even a constant‐phase element (CPE) are promising for simulating highly dynamic processes. By using RCPE elements the impedance spectrum can be modeled with the highest accuracy, which is why this type of model should be used for diagnostic purposes.

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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.

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