Startup Blue Current seeking to commercialize non-flammable fluorinated electrolytes for Li-ion batteries
Lawrence Berkeley National Laboratory (Berkeley Lab) battery scientist Nitash Balsara and co-inventor Joseph DeSimone of the University of North Carolina at Chapel Hill, have launched Blue Current, a startup company backed by investment firm Faster LLC, to commercialize their non-flammable electrolytes for Li-ion batteries.
Conventional alkyl carbonate electrolytes used in lithium-ion batteries are flammable, and incidents of fires have been reported, usually due to thermal runaway. Blue Current’s fluorinated non-flammable electrolytes are functionalized perfluoropolyethers (PFPEs). In addition to their non-flammability, these electrolytes also exhibit high transference numbers and low electrochemical polarization, indicative of longer battery life.
|“Things that contain fluorine don’t burn very easily. They’ll evaporate, but they won’t catch fire.”
The transference number, which quantifies the relative ease with which lithium ions move in electrolytes, is an important parameter that influences battery performance.
In a paper published last year in the Proceedings of the National Academy of Sciences (PNAS), Balsara, DeSimone, and co-authors reported that their PFPE-based electrolytes exhibited thermal stability beyond 200 °C as well as a “remarkably high” transference number of at least 0.91 (more than double that of conventional electrolytes).
|Perfluoropolyethers, first developed in the early 1960s, are a unique and versatile class of lubricants and functional fluids which can be used in many different applications.
|Key properties include low volatility; chemical inertness; high oxidative and thermal stabilities; wide temperature range; non-toxic and biologically inert; and no flash point (non-flammable).
|As a lubricant, PFPE makes its own antiwear additive in the contact region (iron fluoride).
Li/LiNi1/3Co1/3Mn1/3O2 cells made with this electrolyte showed good performance in galvanostatic cycling, confirming the electrolyte’s potential as rechargeable lithium batteries with enhanced safety and longevity.
There is no nonflammable lithium battery on the market today, though others are attempting to make one. Balsara himself co-founded his first battery company, Seeo, in 2007 based on another one of his inventions, a dry polymer electrolyte, which is non-flammable. In December 2014, Seeo announced a major investment from Samsung Ventures (earlier post), but Balsara is no longer directly involved with the company.
Blue Current, based in Berkeley, California, employs three battery scientists and is looking to hire more. Along with Balsara and DeSimone, the third co-founder is Alex Teran, a former graduate student of Balsara’s. The company name was chosen to reflect the safe passage of current through batteries.
Their main challenge now is to improve the conductivity of the PFPE electrolyte. A slow discharge means, for example, that acceleration would be compromised when stepping on the pedal in an electric car.
If there’s a truck coming, you need to accelerate. So while this electrolyte may not be ideal for vehicles at this point, there are other applications where the rate of discharge is not as important.—Nitash Balsara
Blue Current’s engineers are working on modifying the molecular structure of the electrolyte in order to speed up lithium ion motion. Balsara notes that there are uses where the battery does not need to respond in seconds or even minutes. For example, as more people are installing solar panels on their homes, some are thinking about storing that energy for rainy days or nighttime use. “There are applications where safety is not a luxury but a necessity,” Balsara said.
Dominica H. C. Wong, Jacob L. Thelen, Yanbao Fu, Didier Devaux, Ashish A. Pandya, Vincent S. Battaglia, Nitash P. Balsara, and Joseph M. DeSimone (2014) “Nonflammable perfluoropolyether-based electrolytes for lithium batteries” PNAS 111 (9) 3327-3331 doi: 10.1073/pnas.1314615111