Strain-engineered lanthanum-cerium oxide/reduced graphene oxide separators for lithium-sulfur batteries

Lithium‑sulfur (LiS) batteries possess a remarkably high theoretical energy density, yet their commercial application remains limited due to sluggish polysulfide conversion kinetics and the persistent shuttle effect. To address these issues, a composite of La₂Ce₂O₇ and reduced graphene oxide (La₂Ce₂O₇/rGO), derived from a lanthanum-cerium bimetallic metal-organic framework (MOF), was synthesized as a functional separator modifier for LiS batteries. The synergistic interaction between La³⁺ and Ce⁴⁺ induces pronounced lattice distortions, generating numerous catalytically active sites that enable selective adsorption of various polysulfide species. These structural features accelerate the conversion of polysulfides and effectively suppress the shuttle effect. Additionally, the mesoporous architecture of La₂Ce₂O₇ promotes fast lithium-ion (Li⁺) transport, thereby reducing polarization. Benefiting from these advantages, LiS batteries equipped with the La₂Ce₂O₇/rGO modified separator exhibited excellent electrochemical performance. An initial specific capacity of 1264.4 mAh g^-1 at 0.2C was achieved, with 75.5 % capacity retention (955.2 mAh g^-1) after 100 cycles. At 1C, the battery delivered an initial capacity of 1092.6 mAh g^-1 with a minimal capacity fade of ∼0.09 % per cycle. Even under a high sulfur loading of 4.59 mg cm^-2, an initial capacity of 1094.9 mAh g^-1 was maintained. These findings highlight a promising strategy for employing rare-earth-based compounds as efficient polysulfide electrocatalysts in high-performance LiS batteries.