Design of atomic cobalt selenide-doped sulfurized polyacrylonitrile cathode with enhanced electrochemical kinetics for high performance lithium-SPAN batteries

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 471; p. 144581
• Main Authors: Xu, Zhi-Qiang, Zou, Rong, Liu, Wen-Wu, Liu, Guang-Long, Cui, Yun-Shou, Lei, Yi-Xiao, Zheng, Ya-Wen, Niu, Wen-Jun, Wu, You-Zhi, Gu, Bing-Ni, Liu, Ming-Jin, Ran, Fen, Chueh, Yu-Lun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2023
• Subjects: CoSe2-doped sulfuried polyacrylonitrile; Frontier molecular orbital theory (FMO); Gibbs energy barrier; Lithium sulfur batteries; LUMO-HOMO band gap; LUMO-HOMO band gap; Gibbs energy barrier; Frontier molecular orbital theory (FMO); CoSe2-doped sulfuried polyacrylonitrile; Lithium sulfur batteries
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.144581

[Display omitted] •A cobalt selenide doped sulfide polyacrylonitrile (CoSe2@SPAN) is designed as a cathode for Li-SPAN batteries.•Matched-degree of HOMO level of the nucleophilic reagent S2– and LUMO level of the electrophilic reagent Li+ is significantly improved.•The narrowed energy gap between LUMO and HOMO of CoSe2-10@SPAN contributes to the fast reaction kinetics.•Larger Gibbs free energy variation before and after lithiation process promotes the electrochemical reaction. In this work, sulfurized polyacrylonitrile (SPAN) cathodes with atomically dispersed Co and Se active site, namely cobalt selenide doped-sulfide polyacrylonitrile (CoSe2-x@SPAN, x = 6, 10, 15) with different CoSe2 doping concentrations of 6, 10, and 15 wt%, were fabricated by co-heating approach to strengthen the charge conductivity and catalytic activity of SPAN cathode. Atomic scale CoSe2 were doped into the SPAN skeleton to expediating the redox kinetics of lithium storage process, and the catalytic mechanism was made clear by a viewing angle of frontier molecular orbital theory. The DFT calculation results show that CoSe2@SPAN has a more uniform electrostatic potential distribution with a smaller LUMO-HOMO band gap, which is more conducive to electron transport. The Co/Se loaded SPAN polymer constructed by N-Co-S chemical coordination improves the matching degree between the highest occupied molecular orbital (HOMO) of the nucleophile S2− and the lowest unoccupied molecular orbital (LUMO) of the electrophile Li+ during the discharge process, and effectively reduces the bonding orbital σ level of the deposited product Li2S, thereby promoting the lithium storage kinetics of CoSe2@SPAN cathode material and avoiding the shuttle effect. Meanwhile, the larger Gibbs free energy variation during the lithiation process indicates the enhanced reaction kinetics of the CoSe2@SPAN cathode. Ultimately, The Li-SPAN battery with CoSe2-10@SPAN cathode delivers high reversible capacity of 1475 mAh g−1 at 0.2 A/g, superior rate capability and long-term capacity retention of 71.1% after 500 cycles at 1.0 A/g. Accordingly, this study offers insights into the utilization of frontier molecular orbital theory (FMO) to improve the redox kinetics and sulfur utilization of Li-SPAN batteries.