A team of researchers from Stanford University have developed a lithium-ion battery that prevents electronic devices bursting into flames, such as the infamous hoverboard.
The researchers have, for the first time, developed a lithium-ion battery that will shut down before it overheats, causing it to burst into flames. Once it has cooled off, it will then restart.
In a statement, the University wrote: “The new technology could prevent the kind of fires that have prompted recalls and bans on a wide range of battery-powered devices, from recliners and computers, to navigation systems and hoverboards.”
Zhenan Bao, a professor of chemical engineering at Stanford, said:
“People have tried different strategies to solve the problem of accidental fires in lithium-ion batteries. We’ve designed the first battery that can be shut down, and revived over repeated heating and cooling cycles without compromising performance.”
The researchers describe the new battery in a study published in the journal, Nature Energy.
Most lithium-ion batteries consist of two electrodes and a liquid or gel electrolyte, which carries charged particles between them. When the battery is punctured, shorting or overcharged, it generates heat. When the battery reaches approxmailty 300 degrees Fahrenheit (150 degrees Celsius) the electrolyte can catch fire, which could trigger an explosion.
There have been attempts to prevent battery fires, like adding flame retardants to the electrolyte. Stanford engineer, Yi Cui, in 2014 created a “smart battery” that provides ample warning before it gets too hot.
Cui, study co-author, and an associate professor of materials science and engineering, and of photon science, said:
“Unfortunately, these techniques are irreversible, so the battery is no longer functional after it overheats. Clearly, in spite of the many efforts made thus far, battery safety remains an important concern and, requires a new approach.”
The Stanford University wrote in a statement:
To address the problem Cui, Bao, and postdoctoral scholar Zheng Chen turned to nanotechnology. Bao recently invented a wearable sensor to monitor human body temperature. The sensor is made of a plastic material embedded with tiny particles of nickel with nanoscale spikes protruding from their surface.
For the battery experiment, the researchers coated the spiky nickel particles with graphene, an atom-thick layer of carbon, and embedded the particles in a thin film of elastic polyethylene.
Chen, lead author of the study, said:
“We attached the polyethylene film to one of the battery electrodes so that an electric current could flow through it. To conduct electricity, the spiky particles have to physically touch one another.
But, during thermal expansion, polyethylene stretches. That causes the particles to spread apart, making the film nonconductive so that electricity can no longer flow through the battery.”
The University went on to say: “When the researchers heated the battery above 160 F (70 C), the polyethylene film quickly expanded like a balloon, causing the spiky particles to separate, and the battery to shut down.
“But, when the temperature dropped back down to 160 F (70 C), the polyethylene shrunk, the particles came back into contact, and the battery started generating electricity again.”
Bao, who is also a professor of chemistry and materials science and engineering, said:
“We can even tune the temperature higher or lower depending on how many particles we put in or what type of polymer materials we choose. For example, we might want the battery to shut down at 50 C (122 F) or 100 C (212 F).”
To test the stability of new material, the researchers repeatedly applied heat to the battery with a hot-air gun. Each time the battery shut down when it got too hot, and quickly resumed operating when the temperature cooled.
“Compared with previous approaches, our design provides a reliable, fast, reversible strategy that can achieve both high battery performance and improved safety,” Cui said. “This strategy holds great promise for practical battery applications.”
Materials provided by: Stanford University