Journal
JOULE
Volume 3, Issue 1, Pages 136-148Publisher
CELL PRESS
DOI: 10.1016/j.joule.2018.09.024
Keywords
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Funding
- NRCan through its EcoEII program
- NSERC through the Canada Research Chair program
- NSERC through the Discovery Grant program
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The lithium-sulfur battery, despite possessing high theoretical specific energy, faces practical challenges of polysulfide shuttling and low cell-level energy density and hence requires significant functional advances over porous carbon for the cathode host. Here we report the lightweight superconductor MgB2-whose average mass/atom is comparable with carbon-as a metallic sulfur host that fulfills both electron conduction and polysulfide immobilization properties. We show by means of first-principles calculations that borides are unique in that both B-and Mg-terminated surfaces bond exclusively with the S-x(2-) anions (not Li+), and hence enhance electron transfer to the active S-x(2-) 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, we demonstrate sulfur cathodes that achieve stable cycling at a high sulfur loading of 9.3 mg cm(-2).
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