A chemically stabilized sulfur cathode for lean electrolyte lithium sulfur batteries

Sulfur is a promising cathode material for rechargeable lithium batteries due to its high capacity, low cost, abundance, and high sustainability. However, lithium sulfur batteries suffer from poor cycle life and low energy density under lean electrolyte conditions because of the dissolution of lithium polysulfide intermediates. Here, the authors report that the chemical bonding between sulfur and carbon/oxygen in an oxygen-rich dense carbon host can stabilize sulfur and improve the stability of lean electrolyte lithium sulfur batteries. This work opens up a way to develop chemical bonding-stabilized sulfur materials for stable and high-energy lithium sulfur batteries.Lithium sulfur batteries (LSBs) are promising next-generation rechargeable batteries due to the high gravimetric energy, low cost, abundance, nontoxicity, and high sustainability of sulfur. However, the dissolution of high-order polysulfide in electrolytes and low Coulombic efficiency of Li anode require excess electrolytes and Li metal, which significantly reduce the energy density of LSBs. Quasi-solid-state LSBs, where sulfur is encapsulated in the micropores of carbon matrix and sealed by solid electrolyte interphase, can operate under lean electrolyte conditions, but a low sulfur loading in carbon matrix (<40 wt %) and low sulfur unitization (<70%) still limit the energy density in a cell level. Here, the authors significantly increase the sulfur loading in carbon to 60 wt % and sulfur utilization to ~87% by dispersing sulfur in an oxygen-rich dense carbon host at a molecular level through strong chemical interactions of C–S and O–S. In an all-fluorinated organic lean electrolyte, the C/S cathode experiences a solid-state lithiation/delithiation reaction after the formation of solid electrolyte interphase in the first deep lithiation, completely avoiding the shuttle reaction. The chemically stabilized C/S composite retains a high reversible capacity of 541 mAh·g-¹ (based on the total weight of the C/S composite) for 200 cycles under lean electrolyte conditions, corresponding to a high energy density of 974 Wh·kg-¹ . The superior electrochemical performance of the chemical bonding-stabilized C/S composite renders it a promising cathode material for high-energy and long-cycle-life LSBs.

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 01744969
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 30 2020 2:24PM