Nitrogen and iron codoped porous carbon polyhedra for effectively confining polysulfides and efficiently catalyzing their conversion in lithium-sulfur batteries

作者：Yu, Jingping; Khan, Shahzad Ahmad; Zhao, Dengke; Li, Ligui^*; Wu, Zexing; Niu, Xiaojun; Chen, Shaowei

来源：Sustainable Energy & Fuels, 2020, 4(10): 5215-5222.

DOI：10.1039/d0se00942c

• N-C COMPOSITE
• MICROPOROUS CARBON
• FRAMEWORK
• CATHODE
• ANODE
• ELECTROCATALYSTS
• NANOSHEETS
• NANOTUBES
• MOLECULES
• NANOFIBER

Effectively confining lithium polysulfides (LiPSs) and efficiently catalyzing their conversion represent a judicious approach to the preparation of high-rate, long lifespan lithium-sulfur (Li-S) batteries. Herein, an Fe-containing zeolitic imidazolate framework Fe-ZIF-8 is used as a precursor to synthesize a Fe-N-C polyhedron composite that shows a high specific surface area of 1459.3 m(2)g(-1), a large pore volume of 1.037 cm(3)g(-1)and a high nitrogen content of 7.29 at%. Benefiting from the high surface area and polarity of the carbon matrix, the Fe-N-C polyhedron composite can effectively adsorb and confine LiPSs. The S@Fe-N-C based electrode with a high sulfur loading of 72 wt% shows a high initial specific capacity of 1296 mA h g(-1)at 0.1C and can retain a capacity of 450 mA h g(-1)after 500 charge-discharge cycles at 1C, corresponding to a low fading rate of 0.068% per cycle. In contrast, a low capacity of 345 mA h g(-1)is observed for the S@N-C reference electrode even after only 200 cycles. Moreover, the Fe-N-x-C(y)sites within the S@Fe-N-C electrode can also efficiently catalyze the redox conversion of LiPSs during the charge-discharge process, leading to a much higher reversible capacity of 1178 mA h g(-1)at 0.1C, as compared with the 626 mA h g(-1)for the S@N-C electrode. These results support the approach to the preparation of N-doped porous carbons with catalytically active M-N-x-C-y(M is transition metal) sites for high-rate, long-lifespan sulfur cathodes for Li-S batteries.

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