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 x2− anions (not Li +), and hence enhance electron transfer to the active S x2− 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.
Claudiu B. Bucur obtained his Ph.D. in 2008 from Florida State University under the mentorship of distinguished Leo Mandelkern Professor of Polymer Science, Joseph B. Schlenoff. He studied the manner in which polyelectrolyte multilayers assemble, and how doping them with ions changes their mechanical and thermodynamic properties. In 2010 he completed his postdoctoral studies at the USDA Agricultural Research Service Labs, where he investigated corrosion inhibition via biomembranes. Dr. Bucur then joined the Post Lithium Ion Research Group at the Toyota Research Institute of North America, where he focused on metallic anodes such as magnesium, lithium, sodium, and their electrolytes as well as high capacity conversion cathodes such as the sulfur cathode. He expanded upon his experience with polymers, corrosion, and interfaces and was able to advance many areas in the battery field. Currently, Dr. Bucur is Chief Engineer for new battery and solid electrolyte projects at Great Wall Motor, the largest SUV manufacturer in China. He is fascinated by energy storage and dreams of creating the ultimate battery.
View all posts by Claudiu “Bobby” Bucur