Solvent-Dictated Sodium Sulfur Redox Reactions: Investigation of Carbonate and Ether Electrolytes

Huang Zhang,Stefano Passerini,Bingsheng Qin,Thomas Diemant,Huihua Li,R Jürgen Behm

doi:10.3390/en13040836

Abstract

Sulfur-based cathode chemistries are essential for the development of high energy density alkali-ion batteries. Here, we elucidate the redox kinetics of sulfur confined on carbon nanotubes, comparing its performance in ether-based and carbonate-based electrolytes at room temperature. The solvent is found to play a key role for the electrochemical reactivity of the sulfur cathode in sodium–sulfur (Na–S) batteries. Ether-based electrolytes contribute to a more complete reduction of sulfur and enable a higher electrochemical reversibility. On the other hand, an irreversible solution-phase reaction is observed in carbonate solvents. This study clearly reveals the solvent-dependent Na–S reaction pathways in room temperature Na–S batteries and provides an insight into realizing their high energy potential, via electrolyte formulation design.

Highlights

The identification of efficient and effective but low-cost energy storage technologies is still a challenge, preventing the full integration of renewable energy sources into the grid at present.Rechargeable batteries represent one of the best promises for such a target, at least for a number of applications
We systematically investigate the electrolyte solvent on the sulfur redox reaction pathway in room temperature (RT) Na-S batteries, comparing its performance in ether- and carbonate-based electrolytes
In order to address the major problem originating from the insulating nature of sulfur, the sulfur/carbon nanotube (S/CNT) composite was synthesized by a simple melt-diffusion method, which is briefly described in the Experimental section [28]

Summary

Introduction

Rechargeable batteries represent one of the best promises for such a target, at least for a number of applications. Among the most promising electrode materials for such applications is certainly sulfur, which can potentially enable lithium metal anode batteries with about five times higher specific energy compared to current lithium–ion batteries, while being rather inexpensive [1]. The theoretical capacity of a Na–S battery is ~1672 mAh g−1 , based on the sulfur with final product of Na2 S. Despite the success of high-temperature Na–S batteries (>300 ◦ C) for grid-scale application, the problems associated with the solid electrolyte and/or cell sealing integrity failures, resulting in the risk of molten sodium explosive reactions, motivate the exploration for alternatives. The development of room temperature (RT) Na–S batteries with conventional, organic solvent-based

Methods

Results

Conclusion