Sodium-ion batteries: BAM study highlights need for further research on safety
The German Federal Institute for Materials Research and Testing (BAM), together with the European Synchrotron Radiation Facility (ESRF) and the Fraunhofer Institute for High-Speed Dynamics (EMI), investigated the safety of sodium-ion batteries. This battery type is considered a sustainable alternative to lithium-ion batteries. The study’s findings show that established safety mechanisms are not automatically equally effective for all battery technologies, but should be specifically adapted to the chemical composition and cell design of new batteries.
The investigations simulated the mechanical damage of a sodium-ion battery using a so-called nail penetration test. This test is an internationally recognized method for evaluating the safety behavior of batteries. In this test, a cell is intentionally pierced with a metal pin to trigger a critical damage event. The aim was to determine whether the battery—similar to lithium-ion batteries—undergoes a dangerous thermal reaction in which the cell heats up significantly and potentially ignites or explodes, and whether the built-in safety mechanisms function correctly. Due to their resource-efficient materials and potential cost advantages, sodium-ion batteries are considered a promising alternative to lithium-ion systems.
Using high-speed X-ray imaging in a test chamber specially developed by the Fraunhofer Institute for High-Speed Dynamics (EMI), researchers at the European Synchrotron Radiation Facility in Grenoble were able to visualize the internal processes in sodium-ion batteries during a critical event in real time for the first time.
Two other battery types with different safety mechanisms and chemical properties were also examined in direct comparison: a classic lithium-ion battery with a nickel-manganese-cobalt cathode, which is widely used in electric vehicles and portable devices, and a lithium iron phosphate battery. This battery type is considered particularly safe and is frequently used in stationary storage systems.
The results showed clear differences in behavior: The lithium iron phosphate battery proved to be particularly stable. The lithium-ion battery with a nickel-manganese-cobalt cathode reacted in a controlled manner – its safety mechanisms functioned as intended. The behavior of the sodium-ion battery was surprising: It exhibited an almost explosive reaction. However, the cause was not the cell chemistry itself, but a failure of the cell’s venting system, which is designed to relieve overpressure. Due to the rapid pressure increase, the venting system became blocked by other components of the safety devices, leading to the abrupt and violent reaction.
Nils Böttcher, head of the BAM Battery Test Center, explains:
Our investigations show that safety mechanisms cannot simply be transferred from one battery technology to another,
“Especially with new battery types like sodium-ion cells, mechanical components such as venting systems must be specifically adapted and tested. Our results do not call into question the fundamental safety of sodium-ion technology, but they underscore the need to consider chemical composition and safety design together. BAM is therefore actively involved in the development of standards and norms in the field of sodium-ion battery safety.”
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Sodium-ion batteries: BAM study highlights need for further research on safety, source
