Lightweight Metallic MgB2 Mediates Polysulfide Redox and Promises High-Energy-Density Lithium-Sulfur Batteries

By Q. Pang, C. Y. Kwok, Dipan Kundu, X. Liang, L. Nazar. Joule, 2019

269 citations recorded by the source corpus.

Summary 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 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, we demonstrate sulfur cathodes that achieve stable cycling at a high sulfur loading of 9.3 mg cm−2.

Subfields: Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/e77745b30908b6b984468189e9add262482b9e13