Phosphorus doped hierarchical porous carbon nanosheet array as an electrocatalyst to enhance polysulfides anchoring and conversion

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 436; p. 132719
• Main Authors: Kong, Zhenkai, Lin, Yuhang, Hu, Jingwei, Wang, Yanli, Zhan, Liang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.05.2022
• Subjects: Electrocatalysis; Li2S precipitation; Lithium sulfur batteries; Phosphorus doped carbon; Electrocatalysis; Phosphorus doped carbon; Li2S precipitation; Lithium sulfur batteries
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.132719

[Display omitted] •MgO is used as hard template to form hierarchical porous carbon nanosheet array.•Phosphorous doping is introduced by the copolymerization of resorcinol, formaldehyde and phytic acid.•Phosphorous doping exhibits a metal-like LiPSs anchoring effect by forming Li-P and S-P bonds.•Phosphorus doping reduces energy barrier for LiPSs reactions and facilitates Li2S precipitation.•The resultant LSB delivers an excellent capacity and long-term cycling stability. The sluggish redox kinetics and severe lithium polysulfides (LiPSs) shutting effect in lithium sulfur batteries (LSBs) greatly hinder their practical applications. In this work, phosphorus doped carbon nanosheet array (MPC) separator coating layer was synthesized by MgO template, and used as metal-free electrocatalyst to concurrently fulfill efficient polysulfide interception and conversion. By regulating the addition of phytic acid, copolymerization rate of formaldehyde, resorcinol and phytic acid can be conveniently adjusted to form a hierarchical porous MPC microstructure. Phosphorus doping introduces surface defects and enhances the polarity of MPC, which exhibits a metal-like LiPSs anchoring effect by forming Li-P and S-P bonds, avoiding the undesirable oxidation of LiPSs during adsorption. Symmetrical cell and Li2S precipitation experiments reveal that phosphorus doping reduces energy barrier for LiPSs reactions and facilitates Li2S precipitation behavior, exhibiting a strong electrocatalytic effect on Li-S chemistry. Stemming from the above advantages of MPC coated separator, cells exhibit a low interfacial reaction resistance and good anode stability. A capacity of 1161 mAh g−1 at 0.2C and a low attenuation of 0.056% per cycle at 1C over 800 cycles are achieved. For a high sulfur loading up to 4 mg cm−2, the areal capacity can still be stabilized at 2.86 mAh cm−2.