In the context of climate change, mobility is currently undergoing a shift from internal combustion engines to electric motors. The electric engine is currently powered by a traction battery, which in most cases can be classified as lithium-ion technology. This means that electric cars have a very big disadvantage when it comes to recharging. If vehicles can now be filled with fuels such as petrol, diesel or natural gas within a few minutes, the waiting time for conventional charging of a battery system is more than 30 minutes.
In order to reduce this time and thus achieve greater consumer acceptance, processes for the rapid charging of lithium-ion batteries are currently being developed. Practical experience has shown that rapid charging places extreme demands on batteries. They must withstand increased thermal, electrochemical and mechanical stresses, which leads in particular to higher requirements if safe operation and a reduced risk of damage are to be guaranteed in the event of an accident of such battery storage systems.
To increase safety, a module (53 Ah 12s1p) with special fire protection intermediate layers and corresponding sensors was builded up in the project “MoBat” – “Modulare Hochleistungsbatteriesysteme in Verbindung mit sicherer Schnellladetechnik”, which is funded by the “Bundesministerium für Wirtschaft und Energie”. During an abuse test, the values from the sensors were compared with those from a series module that was subjected to the same test. The accident was triggered during the test by overcharging one of the twelve cells. This cell had a State of Charge (SoC) of 120 % at the beginning of the test. The state of charge of the remaining cells in the module was 50 % SoC.
The damage scenario of the accident could be limited to one cell by the fire protection layers used, while in the comparison module without fire protection all cells were damaged by the thermal propagation in the module.