- Internal battery firewall stops overheating before fires start during fault conditions
- Sodium Ion Amp Hour Cells Demonstrate Complete Suppression of Runaway Thermal Reactions
- Three-part safety system improves stability without reducing power production performance
One of the biggest risks of modern batteries is overheating, which can lead to fires, but scientists at the Chinese Academy of Sciences (CAS) say they have developed a sodium-ion battery material that forms a solid internal barrier when temperatures rise, stopping fires before they start.
The dangerous chain reaction it addresses is known as thermal runaway and occurs when heat inside a battery builds up faster than it can escape. Once it starts, temperatures rise rapidly and can cause gas leaks, fires, or explosions.
That failure mode remains one of the biggest safety concerns for electric vehicles and grid-scale storage systems. Preventing the reaction altogether, rather than trying to contain it afterwards, has been a major goal for battery developers.
Article continues below.
A three-part structure
Electric vehicles are often compared to internal combustion engine (ICE) vehicles, which carry gasoline that can ignite if damaged. A battery that stops overheating before it spreads could reduce the risk of fire.
The Chinese research team built what it calls a nonflammable polymerizable electrolyte, or PNE. This liquid transforms into a dense solid when temperatures exceed approximately 302°F (150°C).
That transformation creates an internal layer that blocks the movement of heat between the battery components. In other words, the battery builds its own firewall the moment it starts to overheat.
The researchers described the chemistry behind the system in their work published in Nature. “Here we propose a polymerizable and non-flammable electrolyte, which takes advantage of the synergistic effect of anion-cation solvation and undergoes thermally activated polymerization,” they said.
The safety design works as a three-part structure that supports thermal stability, interface stability, and physical separation within the battery. Each layer plays a role in preventing reactions from spreading once temperatures rise.
The tests were carried out using a 3.5 Ah cylindrical sodium ion battery, a capacity considered significant beyond small laboratory samples.
The researchers reported that this marked the first demonstration of complete suppression of thermal runaway in sodium ion cells at the ampere-hour scale.
During nail penetration testing, the method typically used to simulate internal short circuits, the battery produced no smoke, fire or explosion. The cell also remained stable at temperatures reaching 300°C (572°F).
The researchers reported that security improvements also did not reduce performance levels. The battery achieved an energy density of 211 Wh/kg, which places it within the range expected for advanced sodium-ion systems.
Reliable operation was recorded in temperatures from -40°F to 140°F, covering conditions from the deepest winter to the extreme heat of summer. Voltage stability above 4.3 V was also maintained during the tests.
The researchers say the materials used in the system are already common in industrial production, which could simplify scaling if the technology reaches the commercial manufacturing stage.
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