Advanced Current Collectors with Carbon Nanofoams for Electrochemically Stable Lithium-Sulfur Cells.

Sheng-Heng Chung,Shu-Yu Chen

doi:10.3390/nano11082083

Abstract

An inexpensive sulfur cathode with the highest possible charge storage capacity is attractive for the design of lithium-ion batteries with a high energy density and low cost. To promote existing lithium–sulfur battery technologies in the current energy storage market, it is critical to increase the electrochemical stability of the conversion-type sulfur cathode. Here, we present the adoption of a carbon nanofoam as an advanced current collector for the lithium–sulfur battery cathode. The carbon nanofoam has a conductive and tortuous network, which improves the conductivity of the sulfur cathode and reduces the loss of active material. The carbon nanofoam cathode thus enables the development of a high-loading sulfur cathode (4.8 mg cm−2) with a high discharge capacity that approaches 500 mA·h g−1 at the C/10 rate and an excellent cycle stability that achieves 90% capacity retention over 100 cycles. After adopting such an optimal cathode configuration, we superficially coat the carbon nanofoam with graphene and molybdenum disulfide (MoS2) to amplify the fast charge transfer and strong polysulfide-trapping capabilities, respectively. The highest charge storage capacity realized by the graphene-coated carbon nanofoam is 672 mA·h g−1 at the C/10 rate. The MoS2-coated carbon nanofoam features high electrochemical utilization attaining the high discharge capacity of 633 mA·h g−1 at the C/10 rate and stable cyclability featuring a capacity retention approaching 90%.

Highlights

The increasing demand for an advanced energy storage system has attracted the attention of researchers and inventors, who have investigated the possibility of next-generation rechargeable batteries with a high energy density and low cost [1,2,3]
The graphene-coated and MoS2 -coated carbon nanofoams were prepared by chemical vapor deposition, using carbon nanofoam as the substrate
In the scanning electron microscopy (SEM) images, the unmodified carbon nanofoam appears to have a rough surface composed of nanoporous carbon clusters, with a carbon nanofiber skeleton that supports the continuous conductive network (Figure 1a)

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The carbon nanofoam current collector enables a high sulfur loading of 4.8 mg cm−2 in the cathode, and stabilizes the high-loading sulfur cathode with a high charge storage capacity of 490–452 mA·h g−1 for 100 continuous cycles, indicating an excellent capacity retention of 90% Inspired by these features, we further amplify the material characteristics by modifying the carbon nanofoam with graphene and molybdenum disulfide (MoS2 ) coatings to boost the charge transfer and polysulfide-trapping capabilities, respectively [17,18,19,30,31,32]. In this study, we successfully demonstrate a cell configuration modification with a carbon nanofoam current collector and optimize it with a functional coating

Materials and Chemical Characterization

Electrochemical and Cell Performance Characterization

Material Characterization of the Carbon Nanofoams

Material graphene-coated carbon carbon

Battery