Abstract
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 MgB 2 —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 MgB 2 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 .
Original language | English |
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Pages (from-to) | 136-148 |
Number of pages | 13 |
Journal | Joule |
Volume | 3 |
Issue number | 1 |
DOIs | |
State | Published - Jan 16 2019 |
Externally published | Yes |
Funding
We are grateful for financial support from NRCan through its EcoEII program, and to NSERC for funding through the Canada Research Chair and Discovery Grant programs.
Funders | Funder number |
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Canada Research Chair | |
Natural Sciences and Engineering Research Council of Canada | |
Natural Resources Canada |
Keywords
- batteries
- cathode
- electro-catalysis
- electrochemistry
- energy storage
- lithium-sulfur batteries
- magnesium boride