Years of research and development, precision manufacturing, extreme testing, constant monitoring, and dozens of failsafes all go into preventing thermal runaway in batteries. Now, researchers from the Chinese Academy of Sciences are proposing a shockingly simple solution: batteries that simply cannot catch fire.
Their solution is a sodium-ion battery design that uses a polymerizable, non-flammable electrolyte that rapidly solidifies under extreme heat, forming an internal safety barrier.
Thermal runaway has long been a challenge in battery technology, especially in lithium-ion batteries, which typically use flammable electrolytes. The concern has received an even greater spotlight with the rise in electric vehicle (EV) usage, given the size of the batteries in these vehicles.
This phenomenon is a self-accelerating chain reaction wherein a battery enters an uncontrollable heating state. Once a certain temperature is reached, the battery's internal chemicals begin to react, releasing more heat. This heat then speeds up the reactions, creating even more heat in a vicious cycle. Within milliseconds or minutes, temperatures can skyrocket to 1,292-1,832 °F (700-1,000 °C). This often leads to the release of toxic gases, violent fires, or explosions.
What's more, because the battery creates its own oxygen during this reaction, traditional fire extinguishers often can't put it out. You usually have to wait for the battery to burn itself out. Thermal runaway can be triggered by a variety of conditions, including battery damage, overheating, overcharging, manufacturing defects, exposure to salt water, and external fires.
Sounds really scary, but do not fret. According to EV FireSafe, the chance that your EV will spontaneously combust due to battery issues is about 0.0012%. This figure is possible thanks to really advanced engineering and an immense amount of resources and effort.
Battery manufacturers spend years researching and designing every aspect of the battery, from cell chemistry to electrical architecture. This is usually followed by very precise manufacturing, then several rounds of rigorous testing. In addition to these factors, manufacturers design multiple monitoring, cooling, protective, and failsafe systems around the batteries.
All of these measures require literal years of effort and cost that could easily run into the billions of dollars. Therefore, you can understand why the researchers’ proposed solution, a battery with an inherent fire prevention system, is a significant breakthrough.
Their system is a battery with a built-in smart firewall that automatically prevents potential fires before they start.
Unlike traditional lithium-ion batteries that use flammable liquid electrolytes – typically organic carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate – this new design is sodium-ion based. It features a polymerizable non-flammable electrolyte (PNE). When the battery's internal temperature exceeds 150 °C (302 °F), the liquid electrolyte undergoes a rapid chemical reaction and solidifies. This solid barrier acts as an internal "firewall," physically blocking heat from spreading and cutting off the chain reactions that typically lead to explosions.
In the study published in Nature Energy, the researchers detailed how well the system performed in tests. The battery survived external heating up to 300 °C (572 °F) without triggering thermal runaway. The cell also passed nail penetration tests, simulating an internal short circuit, with complete structural integrity.
And despite the added safety features, the cell maintained a competitive energy density of 211 Wh/kg and operated reliably in temperatures ranging from -40 °C to 60 °C (−40 °F to 140 °F).
Now, the reason for the sodium-ion preference over lithium-ion is straightforward. Sodium-ion systems are inherently more thermally stable. They use less reactive materials, making them far less prone to runaway reactions. This creates an ideal foundation for built-in safety mechanisms like self-solidifying electrolytes.
On the flip side, sodium-ion batteries have lower energy densities, meaning they store less energy per unit volume than their lithium-ion counterparts. However, this is a reasonable price to pay for the system's benefits.
For starters, it eliminates the possibility of a fire. That is a huge win in the safety column. Also, the safety system is passive yet highly effective. You don't need a computer or a cooling pump to "detect" a fire. The battery’s own chemistry acts as a physical fuse.
Additionally, because the battery is inherently safe, it reduces the need for heavy, expensive fireproof "safes" around them. This makes the whole car lighter and cheaper to manufacture.
Some things to note. These polymerizable systems are typically designed as a one-way safety trigger. Once the electrolyte solidifies, it stops ion movement and effectively kills the cell. The paper doesn't explicitly say this, but pack-level repair would likely be required after activation. This is not necessarily a drawback as irreversible shutdown is preferred in safety-critical designs. The firewall is a fail-safe, as batteries are expected to operate well below 150 °C (302 °F).
The system still needs a cooling system. Normal operations still generate heat, and high temperatures can degrade performance and reduce lifespan.
These issues aside, the technology can have far-reaching potential beyond EVs to any system that utilizes batteries.
Source: Chinese Academy of Sciences
