Expedited conversion by using a catalyst has emerged as one of the most effective methods to suppress the shuttle effects in LiÀ S batteries. The application of accelerating conversion through bidirectional catalysts to address the adverse effects of the shuttle effect on batteries has caused extensive concern. Here, bimetallic nickel-cobalt phosphide-based yolk-shell spheres loaded on reduced graphene oxide (NiCo 2 P X /rGO) are designed as bidirectional catalysts, which integrates the merits of NiCo 2 P X and rGO to facilitate the redox reaction kinetics, resulting in rapid deposition during discharging and fast decomposition during charging of the end products (Li 2 S). The porous yolk-shell structure synthesized by the anion exchange method exposes more catalytic sites for massive host-guest interaction. Based on its unique function and structure, the sulfur cathode with NiCo 2 P X /rGO delivers a high capacity of 1238.7 mAh g À 1 at 0.1 C and maintains a stable discharge capacity of 561.1 mAh g À 1 after 400 cycles at 1 C. This study explores the bidirectional catalysis of polysulfides with bimetallic phosphide materials, which provides a new choice for nextgeneration lithium-sulfur batteries.
LithiumÀ sulfur batteries have been regarded as the next generation of competitive batteries because of their high theoretical capacity and energy density. However, the commercial development of lithiumÀ sulfur batteries is restricted by the shuttle action of polysulfides and volumetric expansion of sulfur. Herein, we developed cobalt selenide/carbon cloth composites (CoSe 2 /CC) as the interlayer. CoSe 2 can not only limit the shuttling of polysulfides by CoÀ S bonds and accelerate the catalytic conversion kinetics of sulfur chemistry, but also increases the electrical conductivity of materials, leading to an excellent cycle stability. As a result, the cell with CoSe 2 /CC interlayer has a high initial capacity of 1420 mAh g À 1 at 0.1 C and keeps high-capacity retention of 596 mAh g À 1 after 500 cycles at 1 C rate (70 %). Subsequent electrochemical tests show that CoSe 2 /CC enhance the electrochemical behavior of the polysulfides. Therefore, the hierarchical CoSe 2 /CC composites have promising application potential in lithiumÀ sulfur batteries.
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