Synergizing Lattice Symmetry Breaking and Photoactivation on Oxygen‐Vacancy‐Rich Co 3 O 4 for High‐Performance Photo‐Assisted Lithium‐Sulfur Batteries

Abstract

Lithium–sulfur batteries suffer from intrinsically sluggish polysulfide conversion, in which conventional catalytic designs largely modulate the charge and geometry of transition‐metal sites but leave the spin degree of freedom underexploited. Here, we introduce a dual‐modulation strategy that integrates static oxygen‐vacancy (V o ) engineering with dynamic photoexcitation in V o ‐rich Co 3 O 4 (V o –Co 3 O 4 ), forging a direct link between defect‐induced symmetry breaking and light‐driven catalysis via dynamical reconfiguration of local electronic structure and coordination environment. Spin‐polarized DFT and multiscale characterizations show that V o disrupts the local crystal field around octahedral Co 3+ , triggering a low‐spin → high‐spin crossover and transforming nominally paramagnetic Co 3 O 4 into a room‐temperature ferromagnet with a spin‐polarized interface. Under illumination, photogenerated carriers further modulate the local electronic structure, strengthening Co─S orbital hybridization and depressing the Gibbs free‐energy barrier for the rate‐limiting Li 2 S 4 → Li 2 S 2 step from 0.54 → 0.25 eV. The resulting photo‐assisted Li–S cell delivers 8.6 mAh cm −2 at a sulfur loading of 6.85 mg cm −2 and maintains stable cycling over a wide temperature range of −30°C to 60°C. This work moves beyond conventional d‐band/defect narratives and establishes spin‐polarized interface engineering as a new design that couples defect physics, photonics, and interfacial catalysis.