Safe Electric Vehicle Batteries: PEM Compiles Solutions in White Paper
In a new white paper, the chair "Production Engineering of E-Mobility Components" (PEM) of RWTH Aachen University provides information on current "Challenges and Solutions in Battery Safety". According to the 16-page publication, the failure rate of electric vehicles is between 0.9 and 1.2 per 10,000 such vehicles – compared to 7.3 fire accidents for classic cars with internal combustion engines. "Thermal runaway of lithium-ion batteries releases much less energy than an aequivalent gasoline tank, but the resulting battery fire is much more difficult to extinguish," says PEM director Professor Achim Kampker.
Active and passive safety measures already in use
According to the authors of the white paper, active and passive safety measures are already in use to counter the risk of thermal runaway. Such an event occurs when a battery cell produces more heat than it can dissipate, which can be due to electrical, mechanical or thermal triggers, as well as contamination and manufacturing defects. Once a certain threshold temperature is reached, the runaway is unstoppable and the stored energy is released in the form of heat and flammable gases.
Science and industry are working on barrier materials
"As with most new technologies, research and development is putting a lot of emphasis on improving safety over whatever technology is being replaced or optimized," Kampker says. According to him, the challenge with battery safety lies in its consideration at all levels of cell and battery pack design. In addition to electrical insulation of the individual battery internals, scientists and industry are currently working to prevent the spread of heat during a thermal event at the system level, for example by using barrier materials. In addition, any gas that is generated can be safely discharged by means of a specific form of routing and venting. According to the white paper, on cell level there are also various safety precautions – including power interruption devices and positive temperature coefficient materials –, but they are not equally suitable for all battery types.
System-level and cell-level approach can significantly improve safety
"Battery safety is an ongoing area of research and development," the release says. "The aforementioned safety features and strategies can be used separately, but a multifaceted system-level and cell-level approach can significantly improve the overall operational safety of machines using lithium-ion batteries." According to the authors, thermal protection materials are the primary focus because of their high effectiveness.
The English-language document is available as a free download.