Effects of Anion Mobility on Electrochemical Behaviors of Lithium–Sulfur Batteries

Publication Type

Journal Article

Date Published

10/2017

Abstract

The electrolyte is a crucial component of lithium–sulfur (Li–S) batteries, as it controls polysulfide dissolution, charge shuttling processes, and solid-electrolyte interphase (SEI) layer formation. Experimentally, the overall performance of Li–S batteries varies with choice of solvent system and Li-salt used in the electrolyte, and a lack of predictive understanding about the effects of individual electrolyte components inhibits the rational design of electrolytes for Li–S batteries. Here we analyze the role of the counteranions of common Li salts (such as TfO, FSI, TFSI, and TDI) when dissolved in DOL/DME (1:1 by vol.) for use in Li–S batteries. The evolution of ion–ion and ion–solvent interactions due to various anions was analyzed using 17O NMR and pulsed-field gradient (PFG) NMR and then correlated with electrochemical performance in Li–S cells. These data reveal that the formation of the passivation layer on the anode and the loss of active materials from the cathode (evidenced by polysulfide dissolution) are related to anion mobility and affinity with lithium polysulfide, respectively. For future electrolyte design, anions with lower mobility and weaker interactions with lithium polysulfides may be superior candidates for increasing the long-term stability of Li–S batteries.

Journal

Chemistry of Materials

Volume

29

Year of Publication

2017

Issue

21

Pagination

9023 - 9029

ISSN

0897-4756

Short Title

Chem. Mater.

Refereed Designation

Refereed