Structural and Surfacial Modification of Carbon Nanofoam as an Interlayer for Electrochemically Stable Lithium-Sulfur Cells.

Yee-Jun Quay,Sheng-Heng Chung

doi:10.3390/nano11123342

Abstract

Electrochemical lithium-sulfur batteries engage the attention of researchers due to their high-capacity sulfur cathodes, which meet the increasing energy-density needs of next-generation energy-storage systems. We present here the design, modification, and investigation of a carbon nanofoam as the interlayer in a lithium-sulfur cell to enable its high-loading sulfur cathode to attain high electrochemical utilization, efficiency, and stability. The carbon-nanofoam interlayer features a porous and tortuous carbon network that accelerates the charge transfer while decelerating the polysulfide diffusion. The improved cell demonstrates a high electrochemical utilization of over 80% and an enhanced stability of 200 cycles. With such a high-performance cell configuration, we investigate how the battery chemistry is affected by an additional polysulfide-trapping MoS2 layer and an additional electron-transferring graphene layer on the interlayer. Our results confirm that the cell-configuration modification brings major benefits to the development of a high-loading sulfur cathode for excellent electrochemical performances. We further demonstrate a high-loading cathode with the carbon-nanofoam interlayer, which attains a high sulfur loading of 8 mg cm−2, an excellent areal capacity of 8.7 mAh cm−2, and a superior energy density of 18.7 mWh cm−2 at a low electrolyte-to-sulfur ratio of 10 µL mg−1.

Highlights

Commercial lithium-ion batteries use insertion chemical reaction to reversibly release and store lithium ions between the oxide cathode and the graphite anode
The carbon-nanofoam interlayer inserted between the sulfur cathode and the separator possessed a tortuous and porous carbon network for decreasing the migration of liquid polysulfides and increasing the transfer of electrons and lithium ions in the high-loading sulfur cathodes
Lithium-sulfur cells with a carbon-nanofoam interlayer enabled the cathode to hold a high sulfur content of 70 wt% and a high sulfur loading of 8 mg cm−2, while attaining a high charge-storage capacity of 1087 mAh g−1 at a low electrolyte-to-sulfur ratio of 10 μL mg−1 ; these are the necessary parameters for developing a lithium-sulfur battery cathode with a high energy density

Summary

Introduction

Commercial lithium-ion batteries use insertion chemical reaction to reversibly release and store lithium ions between the oxide cathode and the graphite anode. In mature lithium-ion technology, the charge-storage capacities of lithium-ion battery cathodes have almost reached their theoretical values. To meet the demands of the continuously growing global energy-storage market, the development of next-generation rechargeable batteries requires novel cathode materials featuring a higher charge-storage capacity and long-term electrochemical stability [4,5,6]. Among the newly developed battery chemistries, lithium–sulfur batteries use sulfur as the cathode material to generate a high theoretical charge-storage capacity of 1672 mAh g−1 from a conversion battery chemical reaction, which enables the device to deliver a high energy density of 2600 Wh kg−1 and attain high electrochemical efficiency. Great attention is given to lithium–sulfur cells because of their electrochemical and material properties [7,8,9,10,11]

Methods

Results

Conclusion