d-p-f orbital coupling boosts electrocatalytic sulfur redox for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries hold great promise for high-energy–density energy storage applications but are plagued by the severe shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPSs). We herein report a d-p-f orbital coupling strategy to tackle these critical challenges by incorporating Eu 4f orbitals to activate both metallic (Ni) and non-metallic (Se) sites of NiSe. The imported Eu atoms could induce essential Ni 3d and Se 4p orbital reconstruction through gradient d-p-f coupling, thereby optimizing the band center alignment between NiSe and LiPSs. Such electronic reconstruction strengthens both d-p hybridization between Ni and LiPSs and s-p hybridization between Se and LiPSs, which can not only enhance the chemisorption affinity toward LiPSs but also accelerate interfacial charge transfer kinetics, leading to suppressed shuttle effect and boosted LiPSs conversion kinetics. Therefore, the Li-S batteries assembled with Eu incorporated NiSe deliver exceptional electrochemical performance with a high specific capacity of 896.2 mAh g−1 at 4 C and a retained areal capacity of 5.66 mAh cm−2 under a high sulfur loading of 5.94 mg cm−2 after 100 cycles. This work underscores the critical role of rare-earth 4f orbital coupling for modulating the active sites to construct high-efficiency electrocatalysts for Li-S batteries and beyond.