Lithium-Sulfur Batteries

Rechargeable lithium-sulfur batteries, which use sulfur as the cathode and lithium as the anode, have been the subject of intense research in the recent past due to their high theoretical specific capacity of 1672 mAh/g and energy density of 2600 Wh/kg. However, realization of the high capacity has been precluded by insufficient control and understanding of the sulfur reduction reactions, partly due to the complexity of sulfur and polysulfide (electro)chemistry. We have studied the effects of electrolytes on the charge–discharge performance of rechargeable lithium/sulfur batteries using coin-cells. We found that the solvent in the electrolyte plays a key role in the electrochemical performance of a lithium/sulfur cell while the lithium salt has no significant effects. We also determined that carbonate-based solvents are not appropriate for lithium-sulfur batteries. Using in-situ XAS at the sulfur K-edge, we probed the sulfur reduction intermediates and products in DOL/DME, TEGDME, and EC/DEC solvents and observed a reaction between reduced sulfur species and the carbonate solvent during the course of battery discharge. We also proposed the possible reaction routes based on XAS results.

Citations

  1. Jie Gao, Michael A. Lowe, Yasuyuki Kiya, Héctor D. Abruña. Effects of liquid electrolytes on the charge-discharge performance of rechargeable lithium/sulfur batteries: electrochemical and in-situ X-ray absorption spectroscopic studies. J. Phys. Chem. C, 2011, 115, 25132-25137.