Accelerated Lifetime Testing of Lithium-Ion-Batteries for Faster Approval of New Cell Designs
This project aims at correlating the accelerated lifetime testing of lithium-ion-batteries to the standard testing procedures at nominal conditions. A minimized testing time (≤ 4 months) should also yield the same reliable evaluation of the aging behavior. This approach allows then for reducing the testing from the nowadays usual 12-24 months. Additionally to the reduction in testing time, the resources needed for testing and the time for approving new designs can be minimized. Cyclic and calendaric procedures will be defined and tested for their suitability as accelerated procedure by electrically, chemically and physically characterizing the LIB.
Time intense aging tests are to be abridged in the scope of this project to faster approve new cell designs. Nowadays, those testing procedures usually last longer than two years or until a remaining capacity of 60 % is reached respectively. These long times stem from the application focused testing conditions which cause a slow deterioration rate (e.g. 23 °C) on the one hand and from improving cell quality on the other hand.
This abridging of the testing time is to be achieved by elevating the aging conditions and by an accurate measurement of the relevant parameters which allows to detect an earlier onset of irreversible aging reactions. The common testing times of 8-14 months (cyclic) and 24 months (calendaric) respectively should be reduced to around 4 months. The validity of this will be ensured by predicting known and unknown battery behavior.
In a first step, the data of calendaric (25 °C, 100 % SOC) and cyclic (1C, 100 % DOD and driving cycles) aging tests provided by Volkswagen AG will be analyzed. The abridged tests carried out at ISEA will be compared to these electric and physical-chemical aging results as a benchmark. The cells are industrially produced automotive lithium-ion-batteries.
Having parameterized those first cells, a prediction tool will be developed which will finally be validated by predicting the aging of an unknown cell type.
This project helps to minimize the time needed for validating new cell designs and has thus a direct impact on the costs. This is particularly important for new cell chemistries and long living batteries. Additionally, small and medium sized companies will benefit from these results as their resources for battery testing are limited.
1st August, 2017 to 31st July, 2019