Whether now in the mobile phone, laptop or Navi: when batteries overheat, the device can be quickly broken down. Sometimes even goes on fire. Researchers from Stanford developed a simple but ingenious mechanism which automatically switches off batteries at excessively high temperature after cooling down.
Product recall due to risk of overheating! Too often users of consumer electronics and other devices must send an annoyed again their products, because the batteries are just too hot. Researchers of at Stanford University have now developed an overheating protection for lithium-ion batteries, which prevent destroying battery performance.
It was the first battery, which could be switched off automatically, without long-term performance but also later thrown, explains appeared in nature energy Zhenan Bao, in all Professor of chemical engineering and author of the new study of.
Previous techniques leading to irreversible changes.
In the past, many ways were explored as the one to deal with risk of fire due to overheating. One of them: flame retardants into the batteries. Yi Cui, materials researcher and co-author of the study explains a considerable disadvantage: “Unfortunately all previous techniques are irreversible, so that the batteries will no longer work after that”.
The trick with the graph
For their non-destructive overheating protection, the researchers developed a special polymer film and built up in the cathode of a lithium-ion battery. In that film, the researchers integrated tiny particles on nickel base, that have their outer margins still winger tips in Nano size. Most recently, the nickel particles including the points were covered with graphs. This carbon layer from the, thickness only one atomic layer has a property that the scientists were taking advantage: with increasing heat it expands.
So that electricity can be conducted, the nickel particles have to touch with their tips. The temperature exceeds a certain value (approx. 70 ° C), the Graphene layer themselves puffs so strongly, that she each other pushes away the individual particles and interrupts so physical contact. Episode: The battery turns off. Cools the temperature down, the graphs the nickel particles touch again and start the battery swells off again.
The threshold at which the battery turns off, can be – influenced also variable with a different number of nickel particles, as well as by the kind of the used polymer. According to the researchers, this mechanism can be activated times without compromising the performance of the respective battery permanently.