Princeton University professor Craig Arnold, a specialist in mechanical and aerospace engineering, wants to create batteries that last as long as the gadgets and cars they power.

Scientists and engineers looking at this issue have traditionally approached it from the standpoint of a chemist. What is the battery made of?  Alkaline, nickel, aluminium, lithium?

But Arnold and his graduate student Christina Peabody take a different tack.

"People think of batteries as chemical devices," says Arnold.  "We're looking at how mechanics or physical forces affect the electrochemical performance of the system.  If we can understand why a laptop battery fails, we can start hoping to create one that never needs to be replaced.”

Arnold's research has focused on a physical component of a lithium battery called the "separator".  It's a thin membrane that divides the positive and negative components but allow electrically charged particles to pass through.  As a battery ages, though, Arnold and his team found that the separator lets fewer and fewer particles across, until the battery finally stops working.

"The role of the separator in this sense hadn't really been appreciated before," notes Arnold, who is working on ways to make the separator more efficient.

In this video, Arnold explains his work, comparing a separator to a sponge.

Arnold and Peabody's findings have been published in the Journal of Power Sources.