Safe batteries: Lithium metal batteries with integrated flame retardant
Lithium metal batteries are high-energy, but can quickly catch fire if they overheat. A polymer is designed to prevent this.
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A Chinese research team from the Institute of Chemistry at the Chinese Academy of Sciences has equipped a lithium metal battery with a flame retardant that can prevent fires caused by overheating. Devices equipped with this feature should be better protected against fires.
Lithium metal batteries have an energy density about ten times higher than current lithium-ion batteries. However, these rechargeable energy sources overheat easily, can explode, and catch fire. The danger arises from their composition, as the scientists write in the study “A fire-safe Li metal battery via smart gas management,” which was published in the Proceedings of the National Academy of Sciences (PNAS). According to the study, the lithium metal anodes contained in the batteries can react with the high-voltage nickel-rich oxide cathodes, producing flammable gases. Even a slight overheating can then be enough to trigger a fire or explosion.
Integrated fire protection
The Chinese researchers are addressing the problem by inserting a polymer into the cathode of the battery that releases fire-retardant chemicals when the temperature rises. Nothing happens at operating temperatures. However, if the battery temperature exceeds 100 °C, the polymer decomposes. This releases radicals that prevent a chemical reaction at the anode. As a result, no flammable gases can form.
The researchers tested their battery with the flame retardant and compared it with a conventional lithium metal battery. In their experiments, the scientists gradually increased the temperature of the batteries from 50 °C. Both batteries began to overheat at around 100 °C. The battery with the flame retardant then automatically activated the fire protection system. At 120°C, the conventional battery went out of control and reached a temperature of around 1000°C on its own. It caught fire within 13 minutes. The battery with flame suppression only reached a maximum temperature of 220 °C. The battery did not catch fire or explode.
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The researchers believe that their flame retardant technology can increase the safety of high-energy lithium metal batteries. Until now, they have been used less frequently in devices due to the existing fire hazard. They are also not used in electric cars due to the safety risks. The scientists believe that their integrated flame retardant could make this type of battery suitable for electric cars. The manufacturing process should not be an obstacle. The flame retardant can be integrated into the batteries with only a few changes to the production process.
(olb)
