Photo-Driven Acceleration of Oxidation Kinetics in Aqueous Zinc–Sulfur Batteries

High Resolution Image Download MS PowerPoint Slide Aqueous zinc–sulfur (Zn–S) batteries offer high theoretical energy density and safety but suffer from sluggish solid–solid conversion kinetics during charging (ZnS→S), resulting in high polarization. To overcome this limitation, we introduce a novel photodriven iodine-mediated strategy decoupled from the traditional solid-state transformation energy barrier. By coupling an N-doped anatase/rutile TiO 2 heterojunction (A-TO(N)@R-TO) photoanode with a ZnI 2 electrolyte additive, we achieve ultralow charging voltages and accelerated reaction kinetics. Under illumination, photogenerated holes oxidize I – to I 3 –, which acts as a redox mediator to efficiently oxidize ZnS to S. Simultaneously, photogenerated electrons migrate via the external circuit to reduce Zn 2+ to Zn at the anode. The photovoltage compensates the charging overpotential, reducing the charging voltage from 1.72 to 0.44 V. Energy efficiency increases dramatically from 26% to 125% (output electric energy/input electric energy, not including solar energy). Characterization (PL, XRD, XPS, in situ UV–vis) confirms that the N-doped heterojunction enhances charge separation, while I 3 – promotes ZnS decomposition. The system maintains stable cycling for 80 h at 0.44 V, demonstrating a photochemical cascade mechanism that enables high-efficiency, low-polarization metal–sulfur batteries.