Background:
Increasing the range of battery electric vehicles is of significant interest in the automotive industry. Enhancing the voltage window in which the lithium-ion cell is operating directly affects the driving range of the vehicle but can reduce the cell lifetime. The electrolyte and associated degradation reactions have a significant impact on this parameter. To understand lithium-ion cell aging mechanisms comprehensive electrolyte analysis methods are required.

Results:
A new approach for the gas analysis in industrially produced cells is presented, allowing the identification of the gas amount within the cell and the quantification of the gas composition. By applying this method a comprehensive gas and liquid phase analysis of the electrolyte in large-format automotive cells can be performed to gain insights in the electrolyte degradation process. In a next step the method is applied to perform an electrolyte analysis of lithium-ion cells after long-term cycling. Different cut-off voltages are analyzed to investigate the effect of the voltage window on long-term cycling stability of the electrolyte and identify degradation reactions leading towards capacity loss of the cell.

Significance:
A comprehensive analysis of the gas and liquid phase can be performed to gain further understanding in the electrolyte degradation process. Identifying the suitable voltage window for cycling lithium-ion cells is essential for the development of long lasting battery packs for vehicles with a wide electrical range.