Core-Shell-Structured Sulfur Cathode: Ultrathin δ-MnO2 Nanosheets as the Catalytic Conversion Shell for Lithium Polysulfides in High Sulfur Content Lithium-Sulfur Batteries

Qing Li; Zhipeng Ma; Jiaojiao Li; Zhan Liu; Lukai Fan; Xiujuan Qin; Guangjie Shao

doi:10.1021/acsami.0c09583

Core-Shell-Structured Sulfur Cathode: Ultrathin δ-MnO₂ Nanosheets as the Catalytic Conversion Shell for Lithium Polysulfides in High Sulfur Content Lithium-Sulfur Batteries

ACS Appl Mater Interfaces. 2020 Aug 5;12(31):35049-35057. doi: 10.1021/acsami.0c09583. Epub 2020 Jul 27.

Authors

Qing Li¹, Zhipeng Ma¹, Jiaojiao Li¹, Zhan Liu¹, Lukai Fan¹, Xiujuan Qin¹, Guangjie Shao^{1

2}

Affiliations

¹ Hebei Key Laboratory of Applied Chemistry, Hebei Key Laboratory of Heavy Metal Deep-Remediation in Water and Resource Reuse, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China.
² State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China.

PMID: 32667773
DOI: 10.1021/acsami.0c09583

Abstract

Owing to their low cost and high theoretical energy density, lithium-sulfur (Li-S) batteries are highly promising as a contender for the post-lithium-ion battery era. However, the intrinsic low reversible conversion ability of lithium polysulfides to sulfur/Li₂S during charging/discharging seriously hinders the sulfur utilization, resulting in poor cycling life of batteries. Herein, we report an improvement of core-shell-structured sulfur nanospheres@ultrathin δ-MnO₂ nanosheet electrode materials prepared by a simple precipitation reaction method, in which the ultrathin δ-MnO₂ nanosheets as a catalytic layer can promote the chemical adsorption of lithium polysulfides and their conversion rates to sulfur/L_i2S. Using a combination of the UV-visible adsorption spectra and first-principles calculation, the results indicate that the Mn-O coordination center on the surface of the MnO₂ structure plays an efficient catalytic role in the conversion reaction of lithium polysulfides to insoluble S/Li₂S. The sulfur nanospheres@ultrathin δ-MnO₂ nanosheet composite with a high S mass ratio of 82 wt % reveals a high specific capacity of 846 mA h g^-1 at 1 C rate and good cycling stability. Moreover, the areal capacity of the electrode with a high sulfur loading mass of 10 mg cm^-2 is 5.2 mA h cm^-2, approaching the practical application standard at a current density of 1 mA cm^-2.

Keywords: Li−S batteries; catalytic layer; high sulfur content; δ-MnO2 nanosheets.