Key Figure Based Incoming Inspection of Lithium-Ion Battery Cells

Abstract

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.

Keywords

• lithium-ion batteries
• automotive pouch cells
• cell characterization
• classification
• incoming inspection