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Organic Alkali Metal Salt Derived 3D N-Doped Porous Carbon/ CNTs Composites with Superior Li-S Battery Performance Zhenpu Shi, Yange Yang, Yan Huang, Hongyun Yue, Zhaoxia Cao, Hongyu Dong, Yanhong Yin, and Shu-Ting Yang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b05305 • Publication Date (Web): 17 Jan 2019 Downloaded from http://pubs.acs.org on January 18, 2019
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ACS Sustainable Chemistry & Engineering
Organic Alkali Metal Salt Derived 3D N-Doped Porous Carbon/CNTs Composites with Superior Li-S Battery Performance Zhenpu Shi 123﬩, Yange Yang 123﬩, Yan Huang 123, Hongyun Yue 123*, Zhaoxia Cao 123, Hongyu Dong 123, 1 2
Yanhong Yin 123and Shuting Yang 123*
College of Physics and Material Science, Henan Normal University, Xinxiang Henan 453007, China
National and Local joint Engineering Laboratory of Motive Power and Key Materials, Xinxiang Henan 453007, China; 3
Collaborative Innovation Center of Henan Province for Motive Power and Key Materials, Xinxiang Henan 453007, China) ﬩These
authors contributed equally to this work.
*E-mail:
[email protected];
[email protected];
Abstract The organic alkali metal salt of sodium 4-(methylamino)butanoate has been synthesized and used as precursor for N-doped porous carbon/CNTs composite (NPC/CNTs). The cheap and easy obtained CNTs slurry and metal Na were used as raw materials. NPC provided polysulfides (LiPS) adsorption sites and CNTs constructed the conductive network. The obtained S/NPC/CNTs cathode material which has strong adsorption capacity and high conductivity restrained the shuttle effect to a large extent and enhanced the sulfur utilization, especially at high current density. The synergy of N doping, CNTs adding and mesopores existing enhanced the suppression of shuttle effects. When the S/NPC/CNTs material was used as cathode electrode for Li-S battery, a reversible capacity of 785 mA h g−1 was obtained after 500 cycles, with an average fading rate of 0.08% per cycle at the current density of 0.3 C. The S/NPC/CNTs material also showed superior rate performance, and the specific discharge capacity maintained at 880 mA h g−1 at 2 C rate. Moreover, the single layered pouch cell with a nominal capacity of 200 mA h was assembled and could discharge at a current of 38.6 mA stably. The S/NPC/CNTs cathode material is promising in application of Li-S battery. Keywords: Organic alkali metal salt; N-doped porous carbon; Interconnected CNTs; Sulfur host; LiS battery; Pouch Cell. Introduction
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The increasing power sources demand for mobile electronic equipment has urged the exploration of advanced energy storage devices to replace the conventional lithium-ion batteries (LIBs). [1-3] Among various rechargeable battery systems, the high energy density lithium–sulfur (Li–S) batteries (2600 W h kg−1 in theory) have drawn considerable attention.
[4-6]
Moreover, the elemental sulfur cathode
express high theoretical specific capacity of 1675 mA h g−1, and material is natural abundance and low cost. Despite their great potential advantages, several technical challenges still need to be overcome before the large scale commercialization of Li–S batteries.
[7-9]
The so-called “shuttle effect” is the
major issue associated with Li–S batteries. During cycling processes, the soluble discharge intermediate products polysulfides (LiPS) migrate to the Li anode through the separator.
[10, 11]
The
diffusion and runoff of LiPS lead to low coulombic efficiency, poor cycling stability, and severe selfdischarge. Moreover, the insulated nature of elementary sulfur and its final discharge products (Li2S/Li2S2) blocks the electron transferring, which makes the interruption of the electrochemical reaction.
[12, 13]
In order to overcome the abovementioned challenges associated with Li–S batteries,
encapsulating sulfur into host materials, such as carbonaceous materials, [14, 15] conducting polymers, [16, 17] metal oxides or sulfide,[18] and metal or covalent organic frameworks, [19-21] has been used widely.
Carbonaceous materials are considered as most promising sulfur hosts materials, which can provide the electronic conductive network of sulfur based cathodes and immobilize LiPS.
[9, 22]
Carbon
nanotubes (CNTs) have been extensively used as the sulfur host because of the superior electronic conductivity and mechanical strength. [23, 24] However, the CNTs host with a low specific surface area (typically
