Photocatalysis has been recently incorporated into Li-O₂ battery to mitigate the challenge of high overpotential. However, the structure-activity relationship between photocatalytic materials and charge-discharge mechanisms remains poorly understood. Herein, we propose a photocathode design strategy combining facet engineering and interfacial modulation to regulate the formation and decomposition of Li₂O₂ under illumination. Taking facet-engineered WO₃ as a prototype, we demonstrate that increasing the exposed (002)/(020) facet ratio effectively switches the Li₂O₂ growth pathway from a solution route to a surface growth mode with faster redox kinetics. Notably, the (002) facet exhibits enhanced oxidative capability toward Li₂O₂ decomposition, leading to an ultra-low polarization overpotential of 0.07 V and a high discharge capacity of 10,500 mAh g⁻¹. Furthermore, we reveal that Li₂O₂ possesses intrinsic photoexcitation properties. Based on this, we construct a Z-type WO₃@Li₂O₂ heterojunction to modulate carrier dynamics and facilitate exciton dissociation within Li₂O₂. Benefiting from the enhanced exciton dissociation of Li₂O₂ and improved oxidative capability of photocathode, the battery delivers an ultra-high discharge capacity of 31,800 mAh g^-1 under a current density of 100 mA g^-1. In addition, a low polarization overpotential of 0.04 V is achieved with high reversibility over 1,000 hours. These findings offer mechanistic insights into the photoelectrochemical behavior of Li₂O₂ and establish design principles for high-performance light-assisted Li-O₂ batteries.

Meng Wang, Specially Appointed Researcher of Tohoku University

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