Lightweight Metallic MgB 2 Mediates Polysulfide Redox and Promises High-Energy-Density Lithium-Sulfur Batteries

Quan Pang, Chun Yuen Kwok, Dipan Kundu, Xiao Liang, Linda F. Nazar

Research output: Contribution to journalArticlepeer-review

260 Scopus citations

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 languageEnglish
Pages (from-to)136-148
Number of pages13
JournalJoule
Volume3
Issue number1
DOIs
StatePublished - Jan 16 2019
Externally publishedYes

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.

FundersFunder number
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

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