The service life of lithium-ion batteries is largely determined by the temperature. It is generally known that ageing mechanisms that continuously reduce the available capacity of lithium-ion batteries accelerate in the safe operating window of a battery cell as temperatures rise - and vice versa. In the past, most ageing tests were carried out under homogeneous temperature conditions and thus sometimes differ significantly from the temperature boundary conditions experienced by battery cells in practical applications. In finished battery packs, the individual battery cells are exposed to significant temperature gradients due to cooling systems, for example, and their influence on the service life of the cells has not yet been adequately researched. In the research project 879 I “GradiBatt”, funded by Forschungsvereinigung Antriebstechnik e.V. (FVA), ISEA and the ZSW Ulm are therefore jointly investigating the influence of temperature gradients on the ageing behaviour of lithium-ion battery cells.
In the project, battery cells are controlled under various externally applied temperature gradients and aged in the laboratory in a defined manner. The condition of the cells is monitored by different methods during the ageing tests. To investigate the influence of the temperature gradients in detail, the cells are opened after the ageing tests and the condition of the individual battery components is analysed. Since heterogeneous temperatures within a cell also cause a heterogeneous current distribution, further laboratory experiments are used to investigate how the currents within a battery cell are distributed to the individual electrodes by a heterogeneous temperature distribution. At the end of the project, the findings obtained will be transferred into mathematical models.
01st October 2018 – 31th Septem 2021