2D Cu_{2− x} Se@graphene multifunctional interlayer boosting polysulfide rapid conversion and uniform Li₂S nucleation for high performance Li–S batteries

Abstract Some vital challenges are main obstacles for further development of lithium–sulfur (Li–S) batteries such as low capacity and poor cycle stability resulted from polysulfide shuttling behavior, the physical/chemical entrapment is regarded as an effective method to inhibit and catalyze polysulfides. Herein we design a cross-linked framework of reduced graphene oxide anchored with Cu2−x Se nanoparticles (Cu2−x Se@rGO) by building an electrolyte/Cu2−x Se/graphene triple-phase interface to be a high-efficiency electrocatalyst for Li–S batteries. Importantly, this three-dimensional conductive network possesses a large specific surface area with high ion transport capability, meanwhile providing strong physical constraint for efficient adsorption of soluble polysulfides. Further, this triple-phase catalytic interface provides strong chemical adsorption and abundant Cu2−x Se nanoparticle sulfiphilic active sites, effectively inhibiting the dissolution of polysulfides and guaranteeing the efficient polysulfide adsorption catalysis as well as rapidly uniform Li2S nucleation. Consequently, with the Cu2−x Se@rGO separator, a lower capacity decay rate about 0.059% per cycle after 500 cycles at 2 C is obtained. What’s more, with a higher areal sulfur loading of 3.0 mg cm−2, the capacity is still maintained at 805 mAh g−1 over 100 cycles. Therefore, this work will open new avenue to construct 2D transition metal selenide for superior performance Li–S batteries.