Investigation of thermal behavior of lithium-ion batteries under different operating conditions

In this study, the thermal and electrical performances of composite graphite/PCM battery packs were investigated experimentally. Battery packs with 6S4P cell configuration were used in the experimental investigation. The experiments were carried out for different matrix bulk densities (50 g/L, 75 g/L and 100 g/L), different PCM types (RT-35 and RT-42), different ambient temperatures (-15°C, 25°C and 35°C) and different discharge currents (13.4 A and 30 A). The performances of the composite battery packs and the bare battery pack were compared and discussed. It was observed that there are further improvements in thermal management and electrical performance of graphite/PCM(RT-42) battery packs with high bulk density. These improvements were 21.4% and 68.8% for graphite(100g/L)/PCM(RT-42) battery pack compared to bare battery pack in terms of maximum operating temperature and maximum temperature difference in 25 °C and 30 A performance tests, respectively. Again, the same composite battery pack showed 91%, 91% and 71% superior performance compared to bare battery pack in terms of reliable operating time, capacity and energy capacity in 35 °C and 30 A performance tests, respectively. As a result, it was seen that the use of composite graphite/PCM structures in lithium-ion battery packs significantly increases battery performance, safety and efficiency.