Graphene-Based Three-Dimensional Hierarchical Sandwich-type Architecture for High-Performance Li/S Batteries

• Published in: Nano letters 2013-10, Vol.13 (10), p.4642-4649
• Main Authors: Chen, Renjie, Zhao, Teng, Lu, Jun, Wu, Feng, Li, Li, Chen, Junzheng, Tan, Guoqiang, Ye, Yusheng, Amine, Khalil
• Format: Article
• Language: English
• Subjects: Architecture; Cathodes; Channels; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Current density; Diffusion in nanoscale solids; Diffusion in solids; Electric Power Supplies; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Graphene; Graphite - chemistry; Ions; Lithium - chemistry; Materials science; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Nanotubes, Carbon - chemistry; Physics; Specific materials; Sulfur; Sulfur - chemistry; Three dimensional; Transport properties of condensed matter (nonelectronic); X-Ray Diffraction; X-rays
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl4016683

A multiwalled carbon nanotube/sulfur (MWCNT@S) composite with core–shell structure was successfully embedded into the interlay galleries of graphene sheets (GS) through a facile two-step assembly process. Scanning and transmission electron microscopy images reveal a 3D hierarchical sandwich-type architecture of the composite GS-MWCNT@S. The thickness of the S layer on the MWCNTs is ∼20 nm. Raman spectroscopy, X-ray diffraction, thermogravimetric analysis, and energy-dispersive X-ray analysis confirm that the sulfur in the composite is highly crystalline with a mass loading up to 70% of the composite. This composite is evaluated as a cathode material for Li/S batteries. The GS-MWCNT@S composite exhibits a high initial capacity of 1396 mAh/g at a current density of 0.2C (1C = 1672 mA/g), corresponding to 83% usage of the sulfur active material. Much improved cycling stability and rate capability are achieved for the GS-MWCNT@S composite cathode compared with the composite lacking GS or MWCNT. The superior electrochemical performance of the GS-MWCNT@S composite is mainly attributed to the synergistic effects of GS and MWCNTs, which provide a 3D conductive network for electron transfer, open channels for ion diffusion, strong confinement of soluble polysulfides, and effective buffer for volume expansion of the S cathode during discharge.