High‐Spin 3d Orbital Configuration Driven by Lattice Strain‐Induced Electronic Modulation in Co 4 N/Co 2 P Composites Enables Metal–Sulfur Hybridization for Efficient Polysulfide Conversion

Regulating the spin state of transition metal compounds is crucial for lithium polysulfide conversion in Li–S batteries, yet challenging. Herein, a sea‐urchin‐like Co 4 N/Co 2 P composite is constructed via the in situ introduction of a second phase, where the induced interfacial strain and electronic modulation lead to the formation of high‐spin Co sites, and the composite is further applied as a modified separator. Due to the differences in crystal structure and electronic properties between Co 4 N and Co 2 P, their interfacial contact induces charge redistribution and lattice mismatch, which subsequently generate localized tensile and compressive strains, along with an asymmetric N─Co─P coordination environment, thereby modulating the local electronic structure of Co active sites. Theoretical calculation and in situ characterization confirmed that the synergistic effect of interfacial strain and electronic effects induces d‐orbital spin splitting and energy level rearrangement, increasing unpaired electrons and elevating the spin state of Co. The enhanced spin state strengthens d–p orbital hybridization with sulfur intermediates, accelerating charge transfer and optimizing adsorption behavior. Accordingly, the Co 4 N/Co 2 P‐modified separator battery delivers 1389.4 mAh g −1 at 0.2 C and retains 905.9 mAh g −1 after 100 cycles (0.35% decay per cycle). This work highlights lattice‐strain‐induced spin‐state modulation as an effective strategy for designing high‐performance electrocatalysts.