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Exploring Effective Approach to Synthesize Graphene@sulfur Composites for High Performance Lithium-sulfur Batteries

[ Vol. 14 , Issue. 4 ]

Author(s):

Wu Yang, Wang Yang, Shuanlong Di, Gang Sun and Xiujuan Qin*   Pages 335 - 342 ( 8 )

Abstract:


Background: Due to the high theoretical specific capacity and energy density, lithium– sulfur batteries are regarded as promising next-generation energy storage devices. However, they suffer from rapid capacity fading and poor cyclic stability, which is far from the practical application. Developing an effective sulfur impregnation method is of great importance, especially meeting the demand for large-scale commercial application. In this work, we have prepared reduced graphene oxide (rGO) via microwave method as the host for high-performance sulfur cathode and three methods (melt-diffusion method, chemical precipitation method and chemical precipitation-melt diffusion method) have been explored to synthesize rGO@S composites for high-performance lithium-sulfur batteries.

Method: Graphene oxides (GO) were prepared from natural graphite by modified Hummer’s method. Then reduced graphene oxide (rGO) was synthesized by microwave method. rGO@S composites were prepared by melt-diffusion method, chemical precipitation method and chemical precipitation- melt diffusion method. The galvanostatic charge/discharge measurements and electrochemical impedance spectroscopy were analyzed to obtained the overall performance of lithiumsulfur batteries.

Result: The chemical precipitation-melt diffusion method is an effective strategy to achieve appropriate sulfur encapsulation, where smaller sulfur is impregnated uniformly into abundant pores of rGO matrix. As a result, the CM-rGO@S composite delivers a high initial discharge capacity of 1108.8 mAh g-1 at a current density of 0.2 C, and maintains a stable capacity of 751.3 mAh g-1 after 80 cycles. Furthermore, the CM-rGO@S composite exhibits enhanced cyclic stability and excellent rate capability, delivering a capacity of 598.4 mAh g-1 after 200 cycles at a high current density of 0.5 C with a capacity retention of 65.8%.

Conclusion: In summary, the rGO@S composite prepared by chemical precipitation-melt diffusion method shows outstanding electrochemical performance, such as superior cycle stability and excellent rate capability. It demonstrated that the chemical precipitation-melt diffusion method is an effective strategy to achieve appropriate sulfur encapsulation, where smaller sulfur is impregnated uniformly into abundant pores of rGO matrix. We believe that this attempt can give insights on the other cathode preparation for achieving high performance lithium-sulfur batteries.

Keywords:

lithium-sulfur batteries, synthetic method, sulfur encapsulation, graphene, melt-diffusion method, chemical precipitation method.

Affiliation:

Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004

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