A Bifunctional Perovskite Promoter for Polysulfide Regulation toward Stable Lithium–Sulfur Batteries

Abstract

Lithium-sulfur (LiS) batteries are strongly considered as the next-generation rechargeable cells. However, both the shuttle of lithium polysulfides (LiPSs) and sluggish kinetics in random deposition of lithium sulfides (Li₂S) significantly degrade the capacity, rate performance, and cycling life of LiS cells. Herein, bifunctional Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ perovskite nanoparticles (PrNPs) are proposed as a promoter to immobilize LiPSs and guide the deposition of Li₂S in a LiS cell. The oxygen vacancy in PrNPs increases the metal reactivity to anchor LiPSs, and co-existence of lithiophilic (O) and sulfiphilic (Sr) sites in PrNP favor the dual-bonding (LiO and SrS bonds) to anchor LiPSs. The high catalytic nature of PrNP facilitates the kinetics of LiPS redox reaction. The PrNP with intrinsic LiPS affinity serves as nucleation sites for Li₂S deposition and guides its uniform propagation. Therefore, the bifunctional LiPS promoter in LiS cell yields high rate performance and ultralow capacity decay rate of 0.062% (a quarter of pristine LiS cells). The proposed strategy to immobilize LiPSs, promotes the conversion of LiPS, and regulates deposition of Li₂S by an emerging perovskite promoter and is also expected to be applied in other energy conversion and storage devices based on multi-electron redox reactions.

A bifunctional Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ perovskite is proposed as a promoter to immobilize lithium polysulfides (LiPSs) and guide Li₂S deposition in a working Li–S battery. The coexistence of lithiophilic and sulfiphilic sites in perovskites favors the dual bonding (LiO and SrS bonds) to anchor LiPSs. The Li–S cells with perovskite promoters yield high rate performance and ultralow capacity decay rate.

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