Sunday, October 28, 2018

Drexel enables a Lithium-Sulfur battery evolution

Drexel’s College of Engineering reports that researchers and the industry are looking at Li-S batteries to eventually replace Li-ion batteries because a new chemistry that theoretically allows more energy to be packed into a single battery This improved capacity, on the order of 5-10 times that of Li-ion batteries, equates to a longer run time for batteries between charges.

However, the problem is that Li-S batteries have trouble maintaining their superiority beyond just a few recharge cycles. But a solution to that problem may have been found with new research.

The new approach, reported by in a recent edition of the American Chemical Society journal Applied Materials and Interfaces, shows that it can hold polysulfides in place, maintaining the battery’s impressive stamina, while reducing the overall weight and the time required to produce them.

Lithium-sulfur batteries could be the energy storage devices of the future, if they can get past a chemical phenomenon that reduces their endurance. Drexel researchers have reported a method for making a sulfur cathode that could preserve the batteries' exceptional performance. (Image from Drexel News)
“We have created freestanding porous titanium monoxide nanofiber mat as a cathode host material in lithium-sulfur batteries,” said Vibha Kalra, PhD, an associate professor in the College of Engineering who led the research. “This is a significant development because we have found that our titanium monoxide-sulfur cathode is both highly conductive and able to bind polysulfides via strong chemical interactions, which means it can augment the battery’s specific capacity while preserving its impressive performance through hundreds of cycles. We can also demonstrate the complete elimination of binders and current collector on the cathode side that account for 30-50 percent of the electrode weight — and our method takes just seconds to create the sulfur cathode, when the current standard can take nearly half a day.”

Please find the full report here: LINK
Read the full study here: 

TiO Phase Stabilized into Free-Standing Nanofibers as Strong Polysulfide Immobilizer in Li-S Batteries: Evidence for Lewis Acid-Base Interactions

Arvinder Singh and Vibha Kalra
ACS Appl. Mater. Interfaces, Just Accepted Manuscript
DOI: 10.1021/acsami.8b11029

We report the stabilization of titanium monoxide (TiO) nanoparticles in nanofibers through electrospinning and carbothermal processes and their unique bi-functionality – high conductivity and ability to bind polysulfides – in Li-S batteries. The developed 3-D TiO/CNF architecture with the inherent inter-fiber macropores of nanofiber mats provides a much higher surface area (~427 m2 g-1) and overcomes the challenges associated with the use of highly dense powdered Ti-based suboxides/monoxide materials, thereby allowing for high active sulfur loading among other benefits. The developed TiO/CNF-S cathodes exhibit high initial discharge capacities of ~1080 mAh g-1, ~975 mAh g-1, and ~791 mAh g-1 at 0.1C, 0.2C, and 0.5C rates, respectively with long term cycling. Furthermore, free-standing TiO/CNF-S cathodes developed with rapid sulfur melt infiltration (~5 sec) eradicate the need of inactive elements viz. binders, additional current collectors (Al-foil) and additives. Using postmortem XPS and Raman analysis, this study is the first to reveal the presence of strong Lewis acid-base interaction between TiO (3d2) and Sx2- through coordinate covalent Ti-S bond formation. Our results highlight the importance of developing Ti-suboxides/monoxide based nanofibrous conducting polar host materials for next-generation Li-S batteries. 

"Reprinted with permission from (DOI: 10.1021/acsami.8b11029). Copyright (2018) American Chemical Society."