Synergistic Anode and Cathode Stabilization in Aqueous Zn‐Ion Batteries via a pH‐Stabilizing and Interface‐Adsorbing Additive

Aqueous zinc-ion batteries are a promising next-generation energy storage technology. However, the practical application is severely restricted by issues including dendrite growth, corrosion, the hydrogen evolution reaction of zinc anodes, and the failure of the cathode. Traditional electrolyte engineering mainly focuses on weak acidic environments, while neglecting the alkaline byproducts during calendar aging and operation, as well as the synergistic effects between cathode and anode. Herein, we incorporate 5-Sulfosalicylic Acid (SSA) into ZnSO₄ (ZSO) electrolyte as a multifunctional additive to co-stabilize both electrodes. SSA not only stabilizes the interfacial pH environment through neutralization of alkaline byproducts but also guides the oriented deposition on the Zn (002) plane due to adsorption. Besides, strong acidic chemistry can inhibit the deprotonation of the polyaniline (PANI) cathode, which increases electrochemical performance. The SSA additive improves the Zn plating/stripping reversibility with a Coulombic efficiency around 99.8% at 1 mA cm^-2 for over 2000 h. Besides, the Zn//PANI full cells demonstrate outstanding rate performance and long-term cycling stability, maintaining 72% capacity retention after 1500 cycles at 3 A g^-1. The pouch cells perform well for 200 cycles under high mass loading (8 mg cm^-2) and lean electrolyte (6.25 µL mg^-1) conditions.