Design of organic-inorganic hybrid interfaces for enhanced stability of zinc metal anodes

Zinc (Zn) metal batteries with aqueous electrolytes are promising candidates for large-scale energy storage systems, offering advantages in safety and cost-effectiveness. However, their commercial application remains challenging due to the instability of the Zn/electrolyte interface, primarily caused by the Hydrogen Evolution Reaction (HER) during Zn plating. In this work, the sacrificial additive, a biologically relevant molecule, is introduced to stabilize the Zn anode/electrolyte interface. Possessing a lower reduction potential than water, the sacrificial additive preferentially decomposes to form a robust organic-inorganic hybrid Solid Electrolyte Interphase (SEI) on the Zn anode. This protective layer successfully suppresses HER, mitigates Zn corrosion, and ensures uniform Zn deposition. Computational studies, including molecular dynamics and density functional theory calculations, reveal that the sacrificial additive modifies the Zn²⁺ solvation structure, forming [Zn(H₂O)₄Gly₂]²⁺ complexes that decrease water activity at the anode interface. Electrochemical tests show that symmetric Zn||Zn cells with the modified electrolytes exhibit impressive cycling stability, operating for more than 1000 h at 10 mA cm⁻² with 5 mAh cm⁻² capacity, along with a Coulombic efficiency of 98.2 % after 1000 cycles. Zn||MnO₂ full cells utilizing the modified electrolyte demonstrate excellent long-term cycling stability and enhanced rate performance. These results highlight the potential of low-reduction-potential organic additives in advancing high-performance, durable aqueous Zn-ion batteries.