Revisiting the Role of Conductivity and Polarity of Host Materials for Long‐Life Lithium–Sulfur Battery

• Published in: Advanced energy materials Vol. 10; no. 22
• Main Authors: Lee, Byong‐June, Kang, Tong‐Hyun, Lee, Ha‐Young, Samdani, Jitendra S., Jung, Yongju, Zhang, Chunfei, Yu, Zhou, Xu, Gui‐Liang, Cheng, Lei, Byun, Seoungwoo, Lee, Yong Min, Amine, Khalil, Yu, Jong‐Sung
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.06.2020; Wiley Blackwell (John Wiley & Sons)
• Subjects: Cathodes; Conductivity; cycle stability; Electrode materials; Electrodes; Flux density; Lithium sulfur batteries; mesoporous silica; Polarity; Polysulfides; Silicon dioxide; Sulfur; sulfur hosts
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201903934

Despite their high theoretical energy density and low cost, lithium–sulfur batteries (LSBs) suffer from poor cycle life and low energy efficiency owing to the polysulfides shuttle and the electronic insulating nature of sulfur. Conductivity and polarity are two critical parameters for the search of optimal sulfur host materials. However, their role in immobilizing polysulfides and enhancing redox kinetics for long‐life LSBs are not fully understood. This work has conducted an evaluation on the role of polarity over conductivity by using a polar but nonconductive platelet ordered mesoporous silica (pOMS) and its replica platelet ordered mesoporous carbon (pOMC), which is conductive but nonpolar. It is found that the polar pOMS/S cathode with a sulfur mass fraction of 80 wt% demonstrates outstanding long‐term cycle stability for 2000 cycles even at a high current density of 2C. Furthermore, the pOMS/S cathode with a high sulfur loading of 6.5 mg cm−2 illustrates high areal and volumetric capacities with high capacity retention. Complementary physical and electrochemical probes clearly show that surface polarity and structure are more dominant factors for sulfur utilization efficiency and long‐life, while the conductivity can be compensated by the conductive agent involved as a required electrode material during electrode preparation. The present findings shed new light on the design principles of sulfur hosts towards long‐life and highly efficient LSBs. Despite the nonconducting nature of platelet‐ordered mesoporous silica (pOMS) as a host for sulfur, a pOMS/S composite cathode affords higher reversibility of polysulfides and much less loss of active sulfur during long‐term cycle with outstanding low fading rate. These properties greatly improve both the sulfur utilization efficiency and the cycle performance of Li–S cells.