A Kevlar based barrier between the electrodes in a lithium-ion battery has been developed by the University of Michigan. The development is believed to prevent fires of the kind believed to have grounded Boeing's 787 Dreamliner in 2013.
The barrier is said to stifle the growth of metal tendrils that can become unwanted pathways for electrical current. "Unlike other ultra strong materials, such as carbon nanotubes, Kevlar is an insulator," said Professor Nicholas Kotov. "This property is perfect for separators that need to prevent shorting between two electrodes."
Lithium-ion batteries work by moving lithium ions from one electrode to the other. This creates a charge imbalance and, since electrons cannot pass through a membrane between the electrodes, they go through a circuit instead.
If the holes in the membrane are too big, lithium atoms can create dendrites, similar to the copper dendrite pictured. These can pass through the membrane and if they reach the other electrode, the electrons have a path within the battery. The pores in the Kevlar based membrane are 15 to 20µm in diameter; small enough to block the tips of the dendrites.
Author
Graham Pitcher
Source: www.newelectronics.co.uk