Dual‐Confined Sulfur in Hybrid Nanostructured Materials for Enhancement of Lithium‐Sulfur Battery Cathode Capacity Retention

• Published in: ChemElectroChem Vol. 4; no. 3; pp. 636 - 647
• Main Authors: Zegeye, Tilahun Awoke, Kuo, Chung‐Feng Jeffrey, Chen, Hung‐Ming, Tripathi, Alok Mani, Lin, Ming‐Hsien, Cheng, Ju‐Hsiang, Duma, Alemayehu Dubale, Su, Wei‐Nien, Hwang, Bing‐Joe
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01.03.2017
• Subjects: Carbon; Cathodes; cycle stability; Cycles; Discharge; Graphene; hybrid material; Lithium-sulfur battery; microporous carbon; Nanostructured materials; polysulfide entrapping; Polysulfides; Sulfur; Trapping
• ISSN: 2196-0216; 2196-0216
• DOI: 10.1002/celc.201600696

Herein, we report a dual‐confined sulfur cathode with a nanostructure where sulfur (72.5 wt %) is first encapsulated in microporous carbon (MC) cores and embedded by graphene (G) shells. Larger and soluble polysulfide intermediates (Li2Sx, 4≤x≤8) are trapped by the graphene shells and thus to refrain from dissolution into the organic electrolyte, so that a stable cycling performance can be achieved. Moreover, the graphene shell and hollow space in‐between also help to ensure the integrity of the hybrid cathode against the volume expansion upon cycling. On the other hand, MC confines smaller sulfur molecules (S2‐4) within its small pores and suppresses the formation of soluble polysulfides. The resulting electrode delivers a high initial discharge capacity of 982 mAh g−1 with enhanced capacity retention of 85.4 % after 100th cycles at 0.2 C rates. More importantly, it exhibits a high discharge capacity of 886 mAh g−1, which is maintained at 601 mAh g−1 after 500 cycles at 0.5 C with a coulombic efficiency of nearly 100 %, which is the best performance among reported cycle stabilities. Double bind: A novel strategy of enhancing capacity retention of a carbon‐sulfur cathode is prepared by double confining of sulfur in a microporous carbon‐graphene hybrid with the microporous carbon trapping smaller sulfur (S2‐4) molecules and graphene trapping polysulfide while maintaining good capacity retention.