Cobalt‐Doped SnS2 with Dual Active Centers of Synergistic Absorption‐Catalysis Effect for High‐S Loading Li‐S Batteries

• Published in: Advanced functional materials 2019-02, Vol.29 (8), p.n/a
• Main Authors: Gao, Xuejie, Yang, Xiaofei, Li, Minsi, Sun, Qian, Liang, Jianneng, Luo, Jing, Wang, Jiwei, Li, Weihan, Liang, Jianwen, Liu, Yulong, Wang, Sizhe, Hu, Yongfeng, Xiao, Qunfeng, Li, Ruying, Sham, Tsun‐Kong, Sun, Xueliang
• Format: Article
• Language: English
• Subjects: absorption effects; Carbon nanotubes; Catalysis; Cathodes; Cobalt; cobalt‐doped SnS2; Decay rate; electrocatalyst effects; Electrochemical analysis; high sulfur loading; Li sulfur batteries; Materials science; Polysulfides; Reaction kinetics; Substrates; Sulfur; Tin disulfide
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201806724

The application of Li‐S batteries is hindered by low sulfur utilization and rapid capacity decay originating from slow electrochemical kinetics of polysulfide transformation to Li2S at the second discharge plateau around 2.1 V and harsh shuttling effects for high‐S‐loading cathodes. Herein, a cobalt‐doped SnS2 anchored on N‐doped carbon nanotube (NCNT@Co‐SnS2) substrate is rationally designed as both a polysulfide shield to mitigate the shuttling effects and an electrocatalyst to improve the interconversion kinetics from polysulfides to Li2S. As a result, high‐S‐loading cathodes are demonstrated to achieve good cycling stability with high sulfur utilization. It is shown that Co‐doping plays an important role in realizing high initial capacity and good capacity retention for Li‐S batteries. The S/NCNT@Co‐SnS2 cell (3 mg cm−2 sulfur loading) delivers a high initial specific capacity of 1337.1 mA h g−1 (excluding the Co‐SnS2 capacity contribution) and 1004.3 mA h g−1 after 100 cycles at a current density of 1.3 mA cm−2, while the counterpart cell (S/NCNT@SnS2) only shows an initial capacity of 1074.7 and 843 mA h g−1 at the 100th cycle. The synergy effect of polysulfide confinement and catalyzed polysulfide conversion provides an effective strategy in improving the electrochemical performance for high‐sulfur‐loading Li‐S batteries. The S/NCNT@Co‐SnS2 material acts as not only an effective shuttle‐suppressing shield for polysulfide but also an electrocatalyst in improving sulfur utilization and cycling stability for high‐sulfur‐loading lithium‐sulfur batteries. Therefore, it maintains 1004.3 mA h g−1 after 100 cycles at a current density of 1.3 mA cm−2.