PVP-Assisted Synthesis of Uniform Carbon Coated Li2S/CB for High-Performance Lithium鈥揝ulfur Batteries

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• 作者：Lin Chen ; Yuzi Liu ; Fan Zhang ; Caihong Liu ; Leon L. Shaw
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：November 25, 2015
• 年：2015
• 卷：7
• 期：46
• 页码：25748-25756
• 全文大小：648K
• ISSN：1944-8252

文摘

The lithium鈥搒ulfur (Li鈥揝) battery is a great alternative to the state-of-the-art lithium ion batteries due to its high energy density. However, low utilization of active materials, the insulating nature of sulfur or lithium sulfide (Li₂S), and polysulfide dissolution in organic liquid electrolyte lead to low initial capacity and fast performance degradation. Herein, we propose a facile and viable approach to address these issues. This new approach entails synthesis of Li2S/carbon black (Li2S/CB) cores encapsulated by a nitrogen-doped carbon shell with polyvinylpyrrolidone (PVP) assistance. Combining energy-filtered transmission electron microscopy (EFTEM) elemental mappings, XPS and FTIR measurements, it is confirmed that the as-synthesized material has a structure of a Li₂S/CB core with a nitrogen-doped carbon shell (denoted as Li₂S/CB@NC). The Li₂S/CB@NC cathode yields an exceptionally high initial capacity of 1020 mAh/g based on Li₂S mass at 0.1 C with stable Coulombic efficiency of 99.7% over 200 cycles. Also, cycling performance shows the capacity decay per cycle as small as 0.17%. Most importantly, to further understand the materials for battery applications, field emission transmission electron microscopy (FETEM) and elemental mapping tests without exposure to air for Li₂S samples in cycled cells are reported. Along with the first ever FETEM and field emission scanning electron microscopy (FESEM) investigations of cycled batteries, Li₂S/CB@NC cathode demonstrates the capability of robust core鈥搒hell nanostructures for different rates and improved capacity retention, revealing Li₂S/CB@NC designed here as an outstanding system for high-performance lithium鈥搒ulfur batteries.