ZnSe/N-doped carbon nanoreactor with multiple adsorption sites for stable lithium–sulfur batteries

To commercially realize the enormous potential of lithium–sulfur batteries (LSBs) several challenges remain to be overcome. At the cathode, the lithium polysulfide (LiPS) shuttle effect must be inhibited and the redox reaction kinetics need to be substantially promoted. In this direction, this work proposes a cathode material based on a transition-metal selenide (TMSe) as both adsorber and catalyst and a hollow nanoreactor architecture: ZnSe/N-doped hollow carbon (ZnSe/NHC). It is here demonstrated both experimentally and by means of density functional theory that this composite provides three key benefits to the LSBs cathode: (i) A highly effective trapping of LiPS due to the combination of sulfiphilic sites of ZnSe, lithiophilic sites of NHC, and the confinement effect of the cage-based structure; (ii) a redox kinetic improvement in part associated with the multiple adsorption sites that facilitate the Li+ diffusion; and (iii) an easier accommodation of the volume expansion preventing the cathode damage due to the hollow design. As a result, LSB cathodes based on S@ZnSe/NHC are characterized by high initial capacities, superior rate capability, and an excellent stability. Overall, this work not only demonstrates the large potential of TMSe as cathode materials in LSBs but also probes the nanoreactor design to be a highly suitable architecture to enhance cycle stability.
This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economíay Competitividad through the project SEHTOP, ENE2016-77798-C4-3-R, and ENE2017-85087-C3. D. Yang, C. Zhang, and X. Han thank the China Scholarship Council for the scholarship support. Z. Liang acknowledges funding from a MINECO SO FPI PhD grant (SEV-2013-0295-17-1). J. Li obtained an International Postdoctoral Exchange Fellowship (Talent-Introduction program) in 2019 and is grateful for the project (2019M663468) funded by the China Postdoctoral Science Foundation. The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J. Llorca is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to the ICREA Academia program.