Ferromagnetic Nanoparticle–Assisted Polysulfide Trapping for Enhanced Lithium–Sulfur Batteries

• Published in: Advanced functional materials Vol. 28; no. 20
• Main Authors: Gao, Zan, Schwab, Yosyp, Zhang, Yunya, Song, Ningning, Li, Xiaodong
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 16-05-2018
• Subjects: Cathodes; Cementite; Cotton; Decay rate; Energy storage; ferromagnetic nanoparticles; Ferromagnetism; Flux density; Graphene; Iron carbides; Lithium; Lithium sulfur batteries; Magnetic fields; Materials science; Nanoparticles; Polysulfides; Sulfur; Trapping
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201800563

The lithium–sulfur (Li–S) battery is a promising candidate for next‐generation high‐density energy storage devices because of its ultrahigh theoretical energy density and the natural abundance of sulfur. However, the practical performance of the sulfur cathode is plagued by fast capacity decay and poor cycle life, both of which can be attributed to the intrinsic dissolution/shuttling of lithium polysulfides. Here, a new built‐in magnetic field–enhanced polysulfide trapping mechanism is discovered by introducing ferromagnetic iron/iron carbide (Fe/Fe3C) nanoparticles with a graphene shell (Fe/Fe3C/graphene) onto a flexible activated cotton textile (ACT) fiber to prepare the ACT@Fe/Fe3C/graphene sulfur host. The novel trapping mechanism is demonstrated by significant differences in the diffusion behavior of polysulfides in a custom‐designed liquid cell compared to a pure ACT/S cathode. Furthermore, a cell assembled using the ACT@Fe/Fe3C/S cathode exhibits a high initial discharge capacity of ≈764 mAh g−1, excellent rate performance, and a remarkably long lifespan of 600 cycles using ACT@Fe/Fe3C/S (whereas only 100 cycles can be achieved using pure ACT/S). The new magnetic field–enhanced trapping mechanism provides not only novel insight but unveils new possibilities for mitigating the “shuttle effect” of polysulfides thereby promoting the practical applications of Li–S batteries.
Ferromagnetic Fe/Fe3C nanoparticles with a graphene shell (ACT@Fe/Fe3C/graphene) are successfully embedded into activated cotton textile (ACT) fibers to design a novel host to load sulfur particles. The obtained ACT@Fe/Fe3C/S composite can effectively prevent the dissolution of polysulfides by the spontaneous magnetization of Fe/Fe3C, which can be regarded as a “shielding effect” from the ferromagnetic nanoparticles.