A revolutionary new nanoparticle battery is being developed at Stanford University.
Current lithium-ion batteries can hold a charge for a long time, but pose a significant fire risk. These commonly used batteries, found in a broad range of consumer electronics including smartphones, have been implicated in fires in electric vehicles and cargo planes, as well as smartphones and, most recently, hoverboards. Due to the relatively high risk of overheating, firms and the U.S. government have recalled hundreds of thousands of batteries used to operate cameras, laptops, tablets, cordless tools, navigation systems and more.
Stanford University researchers believe they have invented a solution to the lithium-ion battery overheating problem. A paper published this week in Nature Energy outlines ongoing research on the first lithium-ion nanoparticle battery that automatically shuts down before overheating, but will restart almost instantly when the temperature is reduced.
Statement from study author
“People have tried different strategies to solve the problem of accidental fires in lithium-ion batteries,” explained Zhenan Bao, a professor of chemical engineering at Stanford and study co-author. “We’ve designed the first battery that can be shut down and revived over repeated heating and cooling cycles without compromising performance.”
“The potential for mass production is quite high,” notes Bao, highlighting that the materials are mainly are inexpensive plastic and nickel. She also points out the new nanoparticle battery restarts without a notable loss of efficiency.
More on new lithium-Ion nanoparticle battery
The current lithium-ion battery has two electrodes and a liquid or gel electrolyte that carries charged particles between the electrodes. Any kind of puncture, short or overcharging of the battery leads to the production of heat. Moreover, when the temperature gets close to 300 degrees Fahrenheit (150 degrees Celsius), the electrolyte is likely to catch fire and can lead to an explosion.
Stanford engineering professor Yi Cui, Bao and postdoctoral scholar Zheng Chen turned to nanotechnology to try and solve the problem. Of note, Bao has invented a wearable sensor to monitor human body temperature. The sensor comprises a plastic material embedded with very small particles of nickel with nanoscale spikes on their surface.
The Stanford team coated the spiky nickel particles with graphene (an extremely thin layer of carbon) for their battery tests, and fixed the particles in a thin film of polyethylene.
“We attached the polyethylene film to one of the battery electrodes so that an electric current could flow through it,” said Chen, the lead author of the paper. “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.”
When the battery was heated up to temperatures greater than 160 F (70 C), the polyethylene film rapidly expanded, causing the spiky particles to pull apart and the battery to automatically shut down. However, when the temperature returned to 160 F (70 C), the polyethylene shrank back down to its original size, so the nickel particles with spikes came back into contact, and the battery would produce current again.
“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,” explained Bao, who is also a professor of chemistry and of materials science and engineering. “For example, we might want the battery to shut down at 50 C or 100 C.”