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Waterloo researchers use MgB2 as Li-S battery cathode host to improve performance

Lithium-sulfur (Li-S) batteries, despite their high theoretical specific energy, face practical challenges including polysulfide shuttling and low cell-level energy density.

Researchers at the University of Waterloo have now shown that the lightweight superconductor MgB2 (magnesium diboride)—the average mass/atom of which is comparable with carbon—as a metallic sulfur host fulfills both electron conduction and polysulfide immobilization properties.

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In a paper in the journal Joule the teams reports that, by using first-principles calculations, they found that borides are unique in that both B- and Mg-terminated surfaces bond exclusively with the Sx2− anions (not Li+), and hence enhance electron transfer to the active Sx2− ions.

The surface-mediated polysulfide redox behavior results in a much higher exchange current in comparison with MgO and carbon. By sandwiching MgB2 nanoparticles between graphene nanosheets to form a high-surface-area composite structure, they demonstrated sulfur cathodes that achieve stable cycling at a high sulfur loading of 9.3 mg cm−2.

They conclude that this new avenue toward Li-S cathodes, when coupled with a protected lithium metal anode, may lead to practical implementation of batteries that are lighter, yet robust.

Resources

  • Quan Pang, Chun Yuen Kwok, Dipan Kundu, Xiao Liang, Linda F. Nazar (2018) “Lightweight Metallic MgB2 Mediates Polysulfide Redox and Promises High-Energy-Density Lithium-Sulfur Batteries,” Joule doi: 10.1016/j.joule.2018.09.024

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