Dual-Functional Additive Regulating Zn²⁺ Solvation Structure and (002) Plane-Oriented Deposition for Dendrite-Free Zn Anodes

Aqueous zinc-ion batteries (AZIBs) are expected to be a next-generation electrochemical energy storage system due to their high safety and low cost. However, dendrite growth and side reactions of Zn anodes have significantly hindered the advancement of AZIBs. The present study proposes the use of sulfosalicylic acid (SSA) as a bifunctional additive. First, the solvated structure of Zn²⁺ is reconstructed by SSA through the synergistic effects of its hydroxyl (−OH), carboxyl (−COOH), and sulfonic (−SO₃H) functional groups, effectively inhibiting hydrogen evolution reaction (HER) and other side reactions. Second, the SSA promotes the preferential deposition of Zn²⁺ on the (002) crystal plane through selective adsorption, thereby suppressing the longitudinal growth of Zn and ultimately achieving a dendrite-free Zn anode. Consequently, the Zn anode in the SSA/ZSO electrolyte exhibits a stable cycling capacity of over 2850 h at 1 mA cm⁻², accompanied by a coulombic efficiency of 99.7%. Furthermore, the assembled Zn|CNT/MnO₂ battery demonstrates a capacity retention of 97.7% after 600 cycles, while the Zn||VO₂ battery retains 78% of its capacity after 1100 stable cycles. This further validates the broad applicability and exceptional performance of SSA in different cathode systems. This study offers new insights into the electrolyte design for AZIBs.