Temperature gradient reduction in high-power battery systems using prismatic cells combined with Phase-Change Sheets and Graphite foils

In lithium-ion battery systems thermal management has an important influence on performance, safety and service life. Especially in automotive applications short-term peak loads thermally stress the battery cells. Temperature inhomogeneities arise, effecting ageing rates and electrical properties with the consequences of a reduced system lifetime and diverging state-of-charge of the battery cells. By integration of Phase-Change-Material together with high thermally conductive Pyrolytic Graphite Sheets and graphite gap filler pads, thermal peak shaving and temperature homogenization are implemented to reduce temporal and spatial temperature gradients. In this paper a battery module with prismatic cells and advanced thermal materials was investigated on test-bench. Measurements of temperature rise, differences and distribution at different boundary conditions were performed to evaluate the designed concept. The measured temperature profiles were captured in all three spatial directions within the battery module. As a result, without increasing the volumetric overhead, the maximum rise in temperature was reduced by 13%, while the additional Phase Change Material has 5% of the cells mass. Furthermore the temperature difference on module level was kept below 5K at all conditions above zero degrees ambient temperature even at the maximum specified discharge current and continuous cycling.