Cobalt in Nitrogen-Doped Graphene as Single-Atom Catalyst for High-Sulfur Content Lithium–Sulfur Batteries

• Published in: Journal of the American Chemical Society Vol. 141; no. 9; pp. 3977 - 3985
• Main Authors: Du, Zhenzhen, Chen, Xingjia, Hu, Wei, Chuang, Chenghao, Xie, Shuai, Hu, Ajuan, Yan, Wensheng, Kong, Xianghua, Wu, Xiaojun, Ji, Hengxing, Wan, Li-Jun
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06.03.2019
• Subjects: batteries; catalysts; cobalt; electrochemistry; electrodes; energy; energy density; graphene; X-ray absorption spectroscopy
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.8b12973

Because of their high theoretical energy density and low cost, lithium–sulfur (Li–S) batteries are promising next-generation energy storage devices. The electrochemical performance of Li–S batteries largely depends on the efficient reversible conversion of Li polysulfides to Li2S in discharge and to elemental S during charging. Here, we report on our discovery that monodisperse cobalt atoms embedded in nitrogen-doped graphene (Co–N/G) can trigger the surface-mediated reaction of Li polysulfides. Using a combination of operando X-ray absorption spectroscopy and first-principles calculation, we reveal that the Co–N–C coordination center serves as a bifunctional electrocatalyst to facilitate both the formation and the decomposition of Li2S in discharge and charge processes, respectively. The S@Co–N/G composite, with a high S mass ratio of 90 wt %, can deliver a gravimetric capacity of 1210 mAh g–1, and it exhibits an areal capacity of 5.1 mAh cm–2 with capacity fading rate of 0.029% per cycle over 100 cycles at 0.2 C at S loading of 6.0 mg cm–2 on the electrode disk.