Lithium-ion battery technology continues to experience increases in energy and power density. Its lifetime has to remain the same or to be optimized while changing lithium-ion cell’s properties. Upstream battery cell development is increasingly focusing on the mechanical behavior of the cells to optimize the battery life. Most lithium-ion battery cells are loaded with pressure in state-of-the-art battery modules of battery systems in modern electric vehicles. The external pressure on the cells can contribute to decrease cell’s capacity fade. Still cells experience an inhomogenious degradation due to a irregular current distribution. By applying local pressures on cell’s surface the current distribution inside the cell can be altered and be managed to aim for a homogenious current distribution. A uniform current distribution is expected to homogenize the aging of a cell. Therefore, the local pressure of a cell over lifetime needs to be fully investigated.
In order to investigate the local pressure a test setup is required, which enables to track the pressure of a preloaded cell with sufficient resolution over calendaric or cyclic ageing periods. Requirements for the testbench are a precise adjustment of the default pressure, a spatially resolved pressure measurement and a material with defined stress-strain properties to compensate the swelling of the cell in a predefined pressure range.
This poster presents a test setup to investigate the local pressure of a lithium-ion pouch cell over lifetime. Containing stiff aluminum plates to enable a defined swelling compensation by using compression pads, the integration of pressure sensors into the setup is shown. The adjustment routine of the default pressure is introduced. Additionally, first cyclic and calendaric measurements results are exhibited. Based on measurement results possible surface modification of the aluminum plate to apply a pressure distribution on the cell are presented.