Rational Design of a Bilayer Interface for Long-Term Stability of Zn Anodes and MnO2 Cathodes

Understanding the composition–characteristics–performance relationship of the electrolyte–electric double layer–electrode–electrolyte interface (EEI) is crucial to construct stable EEIs for high-performance aqueous Zn–MnO₂ batteries (AZMBs). However, the interaction mechanisms in AZMBs remain unclear. This work introduces sodium thioctate (ST) into ZnSO₄ electrolyte to construct a stable bilayer EEI on both Zn and MnO₂ electrodes. First, zincophilic ST regulates the solvation structure of hydrated Zn²⁺, suppressing corrosion and the hydrogen evolution reaction. Second, the specific adsorption of ST reconstructs the inner Helmholtz plane, facilitating the desolvation of hydrated Zn²⁺ and homogenizing charge distribution. Finally, ST molecules undergo reversible polymerization at the interface, forming a stable bilayer EEI with a poly(zinc thioctate) outer layer and a ZnS–organic amorphous inner layer, which ensures uniform zinc-ion flux and enhances mechanical stability. Additionally, the dynamic disulfide bonds in ST further enable self-regulation and self-healing of the interface, mitigating damage during cycling. As a result, the ST-enhanced Zn symmetric battery achieves 7800 cycles at 60 mA cm⁻², while the AZMB exhibits only 0.0014% capacity decay over 10 000 cycles at 2000 mA g⁻¹. This bilayer EEI engineering strategy offers effective guidance for the rational design of safe and long-life aqueous zinc-ion batteries.