After months of bad press on everything from hoverboards to potential aeroplane disasters, scientists at Stanford University could have solved the problem of flammable lithium-ion batteries.
Researchers at the US university claim to have developed a lithium battery which automatically shuts down before it gets hot enough to catch fire— and conducts again when the temperature has cooled down.
The breakthrough comes from a material composed of tiny graphene-coated particles of nickel with nanoscale spikes protruding from their surface. These are embedded in a thin film of elastic polyethylene attached to an electrode.
Research leader Zheng Chen said: “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 non-conductive so that electricity can no longer flow through the battery.”
Cut-off mechanisms such as flame retardants and copper separators have been used, but once employed leaves the battery unusable after overheating.
The temperature threshold in the batteries can be adjusted depending on the particular composition of the polymer materials, the research team said.
Picture: Bunched together, as shown here, nanoparticles of graphene-coated nickel conduct electricity