Electrochemically-Triggered Spin Switching Enables Anti-Passivation of Active Sites in Lithium-Sulfur Catalytic...

The irreversible accumulation of insulating Li₂S in lithium-sulfur batteries (LSBs) constitutes a central bottleneck that triggers active-site passivation and performance degradation of catalytic materials. To address the long-standing challenge faced by conventional steady-state catalysts in simultaneously balancing sulfur conversion kinetics and long-term stability, we propose a spin-state-programmable dynamic catalysis strategy. Herein, Zero-strain Wadsley-Roth phase TiNb₂O₇ is employed as a model system. Through a customized catalytic stability evaluation protocol combined with in situ characterization and multiscale kinetic analysis, a π-electron feedback mechanism induced by a reversible Ti⁴⁺/Ti³⁺ transition within the operating voltage window of LSBs is revealed. This mechanism directionally regulates the occupation of Li-S antibonding states of Li₂S, thereby promoting reversible Li₂S dissociation and suppressing interfacial passivation. Enabled by this mechanism, the LSBs maintains 94.6% capacity retention over 240 cycles even at an extreme temperature of -33°C. Furthermore, an energy density of 560 Wh kg^-1 is achieved in pouch cells, which operate stably for 100 cycles. Our study establishes a new materials design principle and mechanistic foundation for simultaneously enhancing activity and stability in sulfur conversion catalytic chemistry.