Safe battery tech prevents “thermal runaway”
If it gets too hot, get out of the battery! Researchers at Stanford University have developed a lithium-ion battery that shuts down automatically as it begins to overheat.
Lithium-ion batteries are used in nearly all portable electronics. They’re light, can store a lot of energy and are easily recharged, but they are also susceptible to overheating if damaged. A short circuit in the battery often leads to fire. A recent article in Nature Energy by a team of Stanford researchers reveals a safe battery design that features “a fast and reversible thermoresponsive polymer switching material that can be incorporated inside batteries to prevent thermal runaway.”
The new Stanford battery uses a polyethylene film that has embedded particles of nickel with nanoscale spikes. Researchers coated the spikes with graphene, a conducting material, so that electricity can flow over the surface. When the temperature rises the film expands, and at about 70 degrees Celsius (160 degrees Fahrenheit) the conducting spikes no longer touch each other, breaking the circuit – causing the battery to shut down.
Once the battery shuts down, the runaway thermal reaction is avoided and the battery cools; eventually the nickel spikes are brought back into contact and the electricity flow resumes.
“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,” said Zhenan Bao, a professor of chemical engineering at Stanford and a member of the research team.
The Nature Energy article [Nature Energy 1, Article number: 15009 (2016) doi:10.1038/nenergy.2015.9] says: “Batteries with this self-regulating material built in the electrode can rapidly shut down under abnormal conditions such as overheating and shorting, and are able to resume their normal function without performance compromise or detrimental thermal runaway. Our approach offers 103–104 times higher sensitivity to temperature changes than previous switching devices.”
This has the potential of averting the catastrophic fires seen in hoverboards, laptops and aircraft.
The article was written by the researchers Zheng Chen, Po-Chun Hsu, Jeffrey Lopez, Yuzhang Li, John W. F. To, Nan Liu, Chao Wang, Sean C. Andrews, Jia Liu, Yi Cui and Zhenan Bao.
Image: Stanford researchers use a polyethylene film in lithium-ion batteries to shut down the battery if it gets too hot. Credit: Stanford University/IDGNS