Full Dissolution of the Whole Lithium Sulfide Family (Li₂S₈ to Li₂S) in a Safe Eutectic Solvent for Rechargeable Lithium–Sulfur Batteries

Abstract

The lithium–sulfur battery is an attractive option for next‐generation energy storage owing to its much higher theoretical energy density than state‐of‐the‐art lithium‐ion batteries. However, the massive volume changes of the sulfur cathode and the uncontrollable deposition of Li2S2/Li2S significantly deteriorate cycling life and increase voltage polarization. To address these challenges, we develop an ϵ‐caprolactam/acetamide based eutectic‐solvent electrolyte, which can dissolve all lithium polysulfides and lithium sulfide (Li2S8–Li2S). With this new electrolyte, high specific capacity (1360 mAh g−1) and reasonable cycling stability are achieved. Moreover, in contrast to conventional ether electrolyte with a low flash point (ca. 2 °C), such low‐cost eutectic‐solvent‐based electrolyte is difficult to ignite, and thus can dramatically enhance battery safety. This research provides a new approach to improving lithium–sulfur batteries in aspects of both safety and performance.

3D Holey Graphene/Polyacrylonitrile Sulfur Composite Architecture for High Loading Lithium Sulfur Batteries

“…For traditional C/S composite electrode (Figure 6f,g), the peaks of S 8 (150, 219, and 474 cm −1 ), Li 2 S 6 (176 and 398 cm −1 ) , Li 2 S 4 (202, 235, and 413 cm −1 ), Li 2 S 2 and Li 2 S can be seen during in situ Raman spectral signal collection process, demonstrating a typical electrochemical reactions from S 8 to Li 2 S and then back to S 8 in traditional Li–S battery system. [ 37–44 ] The results clearly indicate different electrochemical behaviors and intermediate products between 3DHG/PS and traditional C/S electrodes. The polysulfide in 3DHG/PS cathode mainly exists in the form of insoluble Li 2 S during charge/discharge, implying the 3DHG/PS composite architecture could effectively avoid severe shuttling effect of long‐chain polysulfides and therefore realize an excellent cycling stability.…”

Review of Emerging Potassium–Sulfur Batteries

“…These results qualitatively agree with what has been reported for the Li–S system. [ 83,90 ] although the mechanism for K–S has not been worked out.…”

Factors of Kinetics Processes in Lithium–Sulfur Reactions

“…TMU has a relatively high dielectric constant, which is conducive to the dissolution of polysulfide ions and its low viscosity facilitates the ion transport, so as to ensure rapid electrode reaction. Recently, Cheng et al developed ε‐caprolactam/acetamide‐based eutectic‐solvent electrolyte, which can dissolve all lithium polysulfides and lithium sulfide (Li 2 S 8 ‐Li 2 S) . With this new electrolyte, high specific capacity (1360 mAh g −1 ) and reasonable cycling stability are achieved.…”