Utilization of Y-MOF-derived Y2O3/YS@C heterojunction for Li-S battery separators

Abstract

Due to its exceptional energy density and specific capacity, the lithium-sulfur battery is considered one of the most promising energy storage devices. However, the practical use of Li-S batteries is significantly hindered by both the shuttle effect and slow conversion of polysulfides. In order to address the shuttle effect of polysulfides, we utilized a Y-MOF derivative Y₂O₃/YS@C composite material as a modifier layer for Li-S battery separators. Initially, we synthesized Y-MOF by reacting tetra-hydroxyacetate yttrium and isophthalic acid in a solution. Subsequently, we sulfurized the Y-MOF precursor with thioacetamide and heat-treated it at high temperature to obtain Y₂O₃/YS@C composite material. The strong affinity of metal sulfides for sulfur provides chemical anchoring ability for polysulfide, while the heterogeneous structure can couple non-homogeneous regions together to produce synergistic effects and better catalyze polysulfides. By using Y₂O₃/YS@C as a separator modifier, we effectively suppressed the shuttle effect of polysulfides and improved electrochemical performance. At 3 mg cm⁻² sulfur loading, the initial discharge specific capacity of the Y₂O₃/YS@C separator at 0.5 C was 966.1 mAh g⁻¹; after 400 cycles, it still maintained a discharge specific capacity of 530.5 mAh g⁻¹ with a capacity retention rate of 54.9 %. When increasing sulfur loading to 5 mg cm⁻², the first-cycle discharge specific capacity at 0.l C was 831.4 mAh g⁻¹; after 100 cycles, it was still 738.7 mAh g⁻¹, with a capacity retention rate of 88.8 %.