Dual-Affinity Interphase Engineering Enables Stable Aqueous Zn-S Batteries

Aqueous Zn-S batteries have garnered significant attention for grid-scale storage but suffer from rapid capacity fade and sluggish reaction kinetics. Although existing strategies can improve redox reversibility, they fail to fundamentally address capacity attenuation arising from oxidation-driven ZnS decomposition loss. In this study, a nano-copper-based cathode/electrolyte interphase (Cu CEI) featuring a unique sulfur/ZnS dual-affinity is rationally designed to accelerate both S─S and Zn─S bond dynamics, effectively preventing ZnS accumulation and suppressing its decomposition via preferential Cu-ZnS binding. Specifically, the strong binding affinity of the Cu CEI stabilizes ZnS by reducing its direct contact with interfacial water. Meanwhile, the strong interaction between Cu nanoparticles and S₈ activates ring-opening and facilitates S─S bond cleavage, elevating the discharge voltage to 0.75 V. Cu-mediated weakening of Zn─S bonds in ZnS synergistically lowers the apparent activation energy from 69.4 to 29.5 kJ mol^-1, establishing a robust interfacial redox pathway with a low voltage hysteresis of 0.23 V. Consequently, the Cu CEI enables Zn-S system with excellent cycling stability over 1000 cycles at 5 A g^-1 and a high areal capacity of ∼6.5 mAh cm^-2 over 200 h in a pouch cell, underscoring the practical feasibility of this dual-affinity interphase design for high-performance Zn-S batteries.