Encapsulation of Few-Layer MoS2 in the Pores of Mesoporous Carbon Hollow Spheres for Lithium-Sulfur Batteries.

Yunyan Zhao,Zhonghua Zhang,Wenda Li,Qianyu Zhuang,Guicun Li,Hongrui Peng

doi:10.3390/nano9091247

Yunyan Zhao, Zhonghua Zhang + Show 4 more

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https://doi.org/10.3390/nano9091247

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Journal: Nanomaterials	Publication Date: Sep 3, 2019
Citations: 17	License type: CC BY 4.0

Affiliation: Qingdao University of Science and Technology

Abstract

Integrating a highly conductive carbon host and polar inorganic compounds has been widely reported to improve the electrochemical performances for promising low-cost lithium sulfur batteries. Herein, a MoS2/mesoporous carbon hollow sphere (MoS2/MCHS) structure has been proposed as an efficient sulfur cathode via a simple wet impregnation method and gas phase vulcanization method. Multi-fold structural merits have been demonstrated for the MoS2/MCHS structures. On one hand, the mesoporous carbon hollow sphere (MCHS) matrix, with abundant pore structures and high specific surface areas, could load a large amount of sulfur, improve the electronical conductivity of sulfur electrodes, and suppress the volume changes during the repeated sulfur conversion processes. On the other hand, ultrathin multi-layer MoS2 nanosheets are revealed to be uniformly distributed in the mesoporous carbon hollow spheres, enhancing the physical adsorption and chemical entrapment functionalities towards the soluble polysulfide species. Having benefited from these structural advantages, the sulfur-impregnated MoS2/MCHS cathode presents remarkably improved electrochemical performances in terms of lower voltage polarization, higher reversible capacity (1094.3 mAh g−1), higher rate capability (590.2 mAh g−1 at 2 C), and better cycling stability (556 mAh g−1 after 400 cycles at 2 C) compared to the sulfur-impregnated MCHS cathode. This work offers a novel delicate design strategy for functional materials to achieve high performance lithium sulfur batteries.

Highlights

The development of lithium ion (Li-ion) battery technologies cannot meet the ever-growing demand of electric vehicles and automobiles due to their relatively low energy density (387 Wh kg−1 for LiCoO2/C) and their relatively high cost
Several intrinsic problems from sulfur cathodes are impeding the commercial application of lithium-sulfur battery technologies
The intermediated products of lithium polysulfides (Li2Sn, 4 ≤ n ≤ 8) can migrate to the lithium metal anode as its solubility in the organic liquid electrolyte, leading to serious loss of active material, low coulombic efficiency, and poor cycling stability [9,10,11]

Summary

Introduction

The development of lithium ion (Li-ion) battery technologies cannot meet the ever-growing demand of electric vehicles and automobiles due to their relatively low energy density (387 Wh kg−1 for LiCoO2/C) and their relatively high cost. Lithium–sulfur (Li-S) batteries have an ultrahigh theoretical energy density (2600 Wh kg−1) and high theoretical specific capacity of 1675 mA h g−1 based on the multielectron conversion electrochemistry between lithium and elemental sulfur [1,2]. Elemental sulfur, the main cathode material of Li–S batteries, is eco-friendly and low-cost [3]. Considering those factors, Li-S batteries are considered as next-generation high-energy batteries [4,5,6]. The intermediated products of lithium polysulfides (Li2Sn, 4 ≤ n ≤ 8) can migrate to the lithium metal anode as its solubility in the organic liquid electrolyte, leading to serious loss of active material, low coulombic efficiency, and poor cycling stability [9,10,11]

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