Rare-earth-based strategies for lithium-sulfur batteries: enhancing multi-electron conversion reaction kinetics

Lithium-sulfur batteries (LSBs) are considered promising alternatives to conventional lithium-ion batteries (LIBs) because of their high energy density, natural abundance of sulfur, and environmental benignity. Nevertheless, their practical application is hindered by issues including the shuttle effect, severe volume fluctuations, poor conductivity, and lithium dendrite growth at the anode. In recent years, rare-earth (RE) elements, benefiting from their unique unsaturated 4f orbital configurations, have shown great potential in tackling these issues. In particular, RE compounds not only anchor soluble polysulfides via RE-sulfur (S) bonding and catalyze their conversion to S/Li₂S in the cathode, but also improve electrolyte function by facilitating lithium ion (Li⁺) transport, mitigating parasitic reactions, and reinforcing interfacial stability. This review systematically highlights the electronic structures, variable valence states, and strong chemical affinities of RE elements, all of which contribute to their multifunctional roles in LSBs. Furthermore, we summarize the progress of RE-based approaches across different components of LSBs, including cathode hosts, separators/interlayers, electrolyte additives, and solid-state electrolytes. Looking forward, we outline critical challenges and propose emerging directions for leveraging RE-based materials to realize practical, high-performance LSB technologies.