Preventing Battery Explosions

To address problems with smoldering lithium-ion batteries that grounded Boeing’s 787 Dreamliner airplanes, engineers added heat insulation to the batteries and designed the battery box so it will vent any hot gases outside the plane. These fixes won’t stop the batteries from bursting into flames but could mitigate damage if they do.

There may, however, be a chemical solution to these battery woes: swapping their flammable electrolyte solvents for electrolytes that are inherently nonflammable. Joseph M. DeSimone of the University of North Carolina, Chapel Hill, and North Carolina State University spoke about his plans to do just that during a symposium in the Division of Polymer Chemistry at the American Chemical Society meeting in New Orleans on Monday.

Currently, Li-ion batteries use flammable organic solvents, such as ethylene carbonate and ethyl methyl carbonate, for the electrolyte solutions that dissolve the lithium salts. DeSimone, along with coworkers Dominica Wong and Ashish Pandya, believe they’ve come up with an alternative electrolyte that’s just as good at conducting lithium ions but isn’t flammable and can operate efficiently at lower temperatures than current systems.

The new system is based on a mixture of perfluoropolyethers and either poly(ethylene oxide) or polyethylene glycol. DeSimone’s lab reported it was possible to blend such polymers back in 2008 (J. Am. Chem. Soc., DOI: 10.1021/ja803991n).

“Recently, it dawned on us that polyethylene glycol is known to be a good medium to dissolve lithium salts,” DeSimone recalls. So his group began looking into the combination of polyethylene glycol with the perfluoropolyethers as electrolyte solutions for Li-ion batteries.

Adding the perfluoropolyethers to polyethylene glycol solutions of lithium salts has two benefits, DeSimone notes. They’re nonflammable and they drop the temperature at which the polyethylene glycol crystallizes, making the electrolyte solution effective at lower temperatures. DeSimone’s group has been working with Nitash P. Balsara of the University of California, Berkeley, to test the conductivity of these electrolytes and to make prototype batteries. Maintaining high power output in such batteries will be key to success. They’ve also filed patents for the technology.

“DeSimone’s work represents a significant step forward to identify commercially suitable lithium-ion battery electrolyte replacements that will improve the safety of these systems,” comments Dale S. Steichen, vice president of research, development, and innovation with AkzoNobel Surface Chemistry.