Photoinduced Proton-Cation Cascade Boosting Ion Intercalation Dynamics in Photo-Assisted Zinc-Ion Batteries

While photo-assisted ion batteries represent a promising energy storage frontier-with light irradiation significantly improving performance-their development remains hindered by a fundamental knowledge gap, as existing theories struggle to fully account for improved light-driven ion intercalation. This work discovers the photoinduced proton-zinc ion intercalation cascade mechanism, establishing a theoretical framework that explains the synergistic proton-cation interplay and its role in capacity enhancement under illumination. Through light-induced charge transfer, photogenerated electrons drive proton intercalation, which induces the deprotonation of Zn²⁺-coordinated water molecules due to the limited availability of free protons in the electrolyte. This deprotonation is energetically favored because of the lower deprotonation barrier of Zn²⁺-coordinated water compared to uncoordinated water, thereby accelerating zinc-ion desolvation and promoting Zn²⁺ intercalation. Consequently, the synergistic H⁺/Zn²⁺ co-intercalation enables an exceptional areal capacity of 12.86 mA h cm^-2 under illumination in a photo-assisted zinc-ion battery with a high mass-loading of 30 mg cm^-2. This work elucidates a proton-cation cascade mechanism that governs light-driven intercalation dynamics, providing the missing link between photo-excitation and enhanced battery performance.