Sodium fluoride is often added to toothpastes to protect teeth against decay. Now, scientists have found that compounds containing fluorine could power a next-generation battery for electric vehicles. Scientists at the US Department of Energy’s (DOE) Argonne National Laboratory have discovered a fluoride electrolyte which, they say, would increase the range of electric vehicles, and be more safe, because it is nonflammable.
The battery has been described in a paper in Nature Communications.
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While electric vehicles are currently powered by lithium-ion batteries, the new electrolyte will be for lithium metal batteries. Among the alternatives for lithium-ion, one contender battery has an anode (negative electrode) made of lithium metal (lithium-ion batteries use graphite) and a cathode (positive electrode) made of an oxide containing nickel, manganese and cobalt. This offers an energy density that is twice as much as that of a lithium-ion battery. However, this high performance vanishes within less than a hundred cycles of charging and discharging, the Argonne National Laboratory said in a press release.
In typical lithium metal batteries, the electrolyte is a salt of lithium dissolved in a solvent. During the first few cycles of charging and discharging, this electrolyte does not form an adequate protective layer on the anode surface (this layer allows lithium ions to pass in and out freely). This inadequacy is what causes the short cycle-life problem.
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In the new design, scientists have changed the electrolyte. The team of researchers discovered a new fluoride solvent that maintains a robust protective layer for hundreds of cycles. “It couples a fluorinated component that is positively charged (cation) with a different fluorinated component that is negatively charged (anion). This combination is what scientists call an ionic liquid — a liquid consisting of positive and negative ions,” the Argonne National Laboratory explained.
“An exciting new generation of battery types for electric vehicles beyond lithium ion is on the horizon,” the release quoted Zhengcheng (John) Zhang, a group leader in Argonne’s Chemical Sciences and Engineering division, as saying.
