Kevlar is key to fire-preventing lithium ion battery membrane

The University said the innovation is an advanced barrier between the electrodes in a lithium-ion battery. Made with nanofibres extracted from Kevlar the barrier is said to stifle the growth of metal tendrils that can become unwanted pathways for electrical current.

A U-M team of researchers also founded Ann Arbor-based Elegus Technologies to bring this research from the lab to market. Mass production is expected to begin in the fourth quarter 2016.

‘Unlike other ultra strong materials such as carbon nanotubes, Kevlar is an insulator,’ said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Engineering. ‘This property is perfect for separators that need to prevent shorting between two electrodes.’

Lithium-ion batteries work by shuttling lithium ions from one electrode to the other. This creates a charge imbalance, and since electrons can’t go through the membrane between the electrodes, they go through a circuit instead.

However, if the holes in the membrane are too big, the lithium atoms can build themselves into dendrites, which are fern-like structures that eventually push through the membrane. If they reach the other electrode, the electrons have a path within the battery, shorting out the circuit. This is how the battery fires on the Boeing 787 are thought to have started.