The solution to lithium-ion battery flammability problem

The U.S. finds the solution to lithium-ion battery flammability problems.

Due to poor thermal stability and no outstanding electronic control system, lithium-ion batteries are a potential safety hazard for electric vehicles. On the road, except for electric vehicles, consumer electronics products that use the same lithium-ion batteries have flammable characteristics, although they are safe before delivery. Tests, but news such as cell phone batteries exploding is still frequently reported.

Recently, researchers from the University of North Carolina at Chapel Hill (UNCChapelHill), in an experiment known as perfluoro polymer polyether (Perfluoropolyether), found that the material can dissolve lithium salts, which means you can achieve the conductivity of the battery The characteristic, explains researcher Dominica Wong: Most polymers dissolve salts, but this material can. Most importantly, it is not flammable.

Perfluoropolyether, or PFPE, is a liquid-like polymer at room temperature. It has been used for decades as a lubricant for aerospace machinery components. Has good thermal and oxidative stability. But batteries for cellphones, laptops, and electric cars also require electrolytes, which are often made of ion-rich poly dimethyl acetate (DMC).

Lithium-ion batteries are unstable due to the presence of DMC, which is flammable even at room temperature, said Joseph DeSimone, who led the team. So when an electric car is hit, even if there is no fire in the battery, the battery will automatically ignite, turning the car into a reactor. Therefore, if PFPE can replace DMC as the electrolyte, the stability of the battery can theoretically be greatly improved. DeSimone's team did. They mixed PFPE and DMC as the electrolyte for Li-ion batteries and found that not only the thermal stability of the battery was greatly improved, but also the conductivity efficiency was greatly improved. DeSimone also made a point about lithium-air batteries. Li-air batteries have the highest energy density of all Li-ion batteries, one disadvantage is that the electrolyte is often incompatible with oxygen, PFPE may help with this, so lithium-air batteries with the same energy density as gasoline are closer for practicality.

So what exactly is the thermal stability of PFPE batteries? The researchers' experiments show that the batteries can withstand the temperature range of -90℃ to 200℃, which reflects the poor temperature of electric vehicle batteries, and ordinary lithium-ion batteries. The tolerance range is -20℃-60℃. If the temperature is too low or too high, the conductivity will be greatly reduced.

Although PFPE batteries are still a long way from commercialization, it has at least demonstrated that the thermal stability and electrical conductivity of EV batteries are fully feasible.