Bipolar CoSe2 nanocrystals embedded in porous carbon nanocages as an efficient electrocatalyst for Li-S batteries

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-07, Vol.440, p.135820, Article 135820
• Main Authors: He, Li, Yang, Di, Zhao, Hainan, Wei, Luyao, Wang, Dashuai, Wang, Yizhan, Chen, Gang, Wei, Yingjin
• Format: Article
• Language: English
• Subjects: Cobalt selenide; Electrode kinetics; First-principles calculations; Host material; Lithium-sulfur battery
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.135820

•CoSe2 (111) surface possesses adjacent nucleophilic and electrophilic centers.•The decomposition energy barriers of Li2S on CoSe2 surface are decreased.•CoSe2 nanocrystals with (111) surface are prepared.•CoSe2 improves the affinity toward polysulfide and accelerates its conversion. The confinement and catalysis properties of orthorhombic CoSe2 as a host material for Li-S battery are studied by theoretical and experimental methods. First-principles calculations show that the (111) surface of CoSe2 possesses adjacent nucleophilic and electrophilic centers. This bi-polar surface can easily bond the polysulfide molecules and catalyze their conversion reactions. As a result, the decomposition energy barriers of polysulfides are greatly decreased from ∼3.0 eV to 0.2–0.4 eV. Following theoretical prediction, CoSe2 nanocrystals with specific (111) surface are prepared and embedded in porous carbon nanocages using ZIF-67 metal organic framework as a template. Benefited from the advantages of porous C and CoSe2 (111) surface, the shuttling of polysulfides is suppressed and their conversion kinetics is facilitated. The Li-S cell using this host material exhibits high capacity and remarkable cycle stability, showing a discharge capacity of 1199 mA·h·g−1 at 0.2C and 400 stable cycles at 1.0C.