A Lithium Ion Battery Design That Can’t Catch Fire

Researchers at the University of North Carolina at Chapel Hill have created a nonflammable lithium-ion battery. A lithium-based battery that simply isn’t ignitable would solve a major problem that the lithium chemistry experiences from small portable electronics to reports of Tesla Model S automobiles and the surprising lithium battery fires in Boeing 787 Dreamliners.  For all the intense effort in engineering and manufacturing care the chemistry is problematic.

Chemist Joseph DeSimone at the University of North Carolina at Chapel Hill (UNC) leads research beginning with the study of a material that prevents marine life from sticking to the bottom of ships.  From there the team identified a surprising replacement for the only inherently flammable component of today’s lithium-ion batteries: the electrolyte.

The UNC work published yesterday in the Proceedings of the National Academy of Sciences.  The technological insight shows a way for developing a new generation lithium-ion battery that doesn’t spontaneously catch fire at high temperatures. The discovery has the potential to renew consumer confidence in a technology that has attracted significant concern – particularly after the lithium battery fires in Boeing 787 Dreamliners and Tesla Model S vehicles.

DeSimone, Chancellor’s Eminent Professor of Chemistry in UNC’s College of Arts and Sciences and the William R. Kenan Jr. Distinguished Professor of Chemical Engineering at N.C. State University and of Chemistry at UNC explains the background, “There is a big demand for these batteries and a huge demand to make them safer. Researchers have been looking to replace this electrolyte for years, but nobody had ever thought to use this material called perfluoropolyether, or PFPE, as the main electrolyte material in lithium-ion batteries before.”

The situation today has lithium-ion batteries powering everything from our mobile devices – phones, tablets and laptops – to jumbo airliners and plug-in electric cars.  They all have an inherently flammable liquid used as the electrolyte.  The lithium ions shuttle through this liquid from one electrode to the other when the battery is being charged. But when the batteries are overcharged, the electrolyte can catch fire and the batteries can spontaneously combust.  For all the design and engineering prowess, the manufacturing precision and professionalism just one tiny mistake can cause a fire.

Spontaneous combustion is not so much a problem with mobile devices, which are small and replaced frequently, explains Dominica Wong, a graduate student in DeSimone’s lab who spearheaded the project. But when the batteries are scaled up for use in electric cars or planes, their flammability problems are magnified and the consequences can be catastrophic.

In the past, researchers have identified alternative nonflammable electrolytes for use in lithium-ion batteries, but these alternatives compromised the properties of the lithium ions.

Wong sums up the UNC material saying, “In addition to being nonflammable, PFPE exhibits very interesting properties such as its ion transport. That makes this electrolyte stand apart from previous discoveries.”

Previously researchers have identified alternative nonflammable electrolytes for use in lithium-ion batteries, but these alternatives compromised the properties of the lithium ions.

The background begins when DeSimone realized that PFPE, a material that he had been researching for the Office of Naval Research to prevent marine life from sticking to the bottom of ships, had a similar chemical structure to a polymeric electrolyte commonly studied for lithium-ion batteries. PFPE is nothing new; it’s a polymer that has long been used as a heavy-duty lubricant to keep gears in industrial machinery running smoothly.

“When we discovered that we could dissolve lithium salt in this polymer, that’s when we decided to roll with it,” said Wong. “Most polymers don’t mix with salts, but this one did – and it was nonflammable. It was an unexpected result.”

A wonderful and serendipitous result would be more on point.

Collaborator Nitash Balsara, faculty senior scientist at Lawrence Berkeley National Laboratory and professor of chemical and biomolecular engineering at the University of California, Berkeley, and his team were then tasked with studying lithium-ion transport within the electrolyte and found compatible electrodes to assembly a battery.

Looking ahead the team will focus on optimizing electrolyte conductivity and improving battery cycling characteristics, which are necessary before the new material can be scaled up for use in commercial batteries, explains Wong. If successful, a commercial battery can also be used in extremely cold environments, such as for aerospace and deep-sea naval operations.

Wong said, “This is a really good starting point for us to go in a lot of different directions and bridge the gap between academic research and industrial scale-up. But the best part was the interdisciplinary collaboration – having the opportunity to work on scientific problems with researchers with different backgrounds and expertise.”

As much as the team seems to like the relationship experience in the work and it’s a very refreshing and respectable attitude, the rest of us are quite interested in the potential.  The remaining questions do not look to be showstoppers, and the potential additive packages for improving conductivity and cycling might well be opportunities in themselves.

Today has been a good day for the battery consumers.

Source: http://newenergyandfuel.com/http:/newenergyandfuel/com/2014/02/11/a-lithium-ion-battery-design-that-cant-catch-fire/