Asymmetric P, N-coordinated Mo single atoms coupled with atomic clusters for synergistic sulfur redox in LiS batteries

The sluggish redox kinetics and severe shuttle effect of lithium polysulfides (LiPSs) remain critical challenges for practical lithium‑sulfur (Li S) batteries. Herein, we report a dual-site catalytic architecture featuring asymmetrically coordinated Mo single atoms (Mo-P 3 N 1 ) and Mo atomic clusters co-anchored on an N, P-doped carbon matrix (Mo-NPC/Mo AC). Distinct from conventional symmetric M-N 4 single-atom structures, the introduction of P coordination breaks the geometric symmetry and induces electronic polarization of Mo centers, leading to an upshifted d-band center and enhanced LiPSs adsorption capability. Comprehensive synchrotron X-ray absorption spectroscopy combined with wavelet transform analysis directly confirms the coexistence of atomically dispersed Mo sites and Mo Mo coordinated clusters. Through electrochemical kinetic analysis and density functional theory calculations, we reveal a directionally decoupled catalytic mechanism: Mo-NPC single atoms predominantly accelerate the rate-determining solid-state conversion of Li 2 S 4 to Li 2 S during discharge, while Mo atomic clusters effectively lower the energy barrier for Li 2 S decomposition during charge. This full redox-cycle-oriented synergistic catalysis significantly reduces polarization and accelerates sulfur conversion kinetics. Benefiting from the integrated effects of electronic structure modulation, dual-site catalytic cooperation, and hierarchical porous confinement, Li S batteries employing Mo-NPC/Mo AC functionalized separators deliver an initial specific capacity of 1081 mAh g −1 at 1C, with a low capacity decay rate of 0.074% per cycle over 650 cycles, together with remarkable rate capability up to 4C. This work establishes a mechanistically clarified dual-site catalytic model for regulating the complete sulfur redox pathway and provides new insights into rational catalyst design for high-performance Li S batteries.