Chinese researchers develop sodium-ion battery design that forms internal heat barrier to stop thermal runaway reactions linked to battery fires
- Internal battery firewall stops overheating before fires begin during failure conditions
- Ampere-hour sodium-ion cells demonstrate complete suppression of thermal runaway reactions
- Three-part safety system improves stability without reducing energy output performance
One of the biggest risks in modern batteries is overheating which can lead to fires, but scientists at the Chinese Academy of Sciences (CAS) claim to have developed a sodium-ion battery material that forms a solid internal barrier when temperatures rise, stopping fires before they begin.
The dangerous chain reaction it addresses is known as thermal runaway, and it happens when heat inside a battery builds faster than it can escape. Once it starts, temperatures rise quickly and can lead to gas release, fire, or explosions.
That failure mode remains one of the biggest safety concerns for electric vehicles and grid-scale storage systems. Preventing the reaction entirely, rather than trying to contain it afterward, has been a major goal for battery developers.
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A three-part structure
Electric vehicles are often compared with internal combustion engine (ICE) vehicles, which carry gasoline that can ignite if damaged. A battery that stops overheating before it spreads could reduce fire risk.
The Chinese research team built what it calls a polymerizable non-flammable electrolyte, or PNE. This liquid changes into a dense solid when temperatures exceed about 302°F (150°C).
That transformation creates an internal layer that blocks heat movement between battery components. In other words, the battery builds its own firewall at the moment overheating starts.
Researchers described the chemistry behind the system in their work published in Nature. “Here we propose a polymerizable and non-flammable electrolyte, which leverages the synergistic anion-cation solvation effect and undergoes thermally triggered polymerization,” they said.
The safety design works as a three-part structure that supports thermal stability, interface stability, and physical separation inside the battery. Each layer plays a role in preventing reactions from spreading once temperatures build.
Testing was carried out using a 3.5Ah cylindrical sodium-ion battery, a capacity considered meaningful beyond small laboratory samples.
The researchers reported that this marked the first demonstration of complete thermal runaway suppression in ampere-hour-scale sodium-ion cells.
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 572°F (300°C).
Researchers reported that safety gains did not reduce performance levels either. The battery achieved an energy density of 211Wh/kg, placing it within the expected range for advanced sodium-ion systems.
Reliable operation was recorded across temperatures from -40°F to 140°F, covering conditions from deep winter to extreme summer heat. Voltage stability above 4.3V was also maintained during testing.
The researchers say the materials used in the system are already common in industrial production, which could simplify scaling should the technology reach the commercial manufacturing stage.
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