Interfacial Adsorption Layers Based on Amino Acid Analogues to Enable Dual Stabilization toward Long-Life Aqueous Zinc Iodine Batteries

Abstract

Aqueous zinc–iodine (Zn–I₂) batteries are promising candidates for large-scale energy storage due to the merits of low cost and high safety. However, their commercial application is hindered by Zn corrosion and polyiodide shuttle at I₂ cathode. Herein, N,N-bis(2-hydroxyethyl)glycine (BHEG) based interfacial adsorption layers are constructed to stabilize Zn anodes and mitigate polyiodide shuttle according to ion–dipole interactions, by using a strategy of electrolyte additive. The tertiary amine (N(CH₂)₃) and carboxyl (─COO⁻) groups in the deprotonated BHEG can reversibly capture H⁺ and dynamically neutralize OH⁻ ions, efficiently buffering the interfacial pH of Zn metal anodes and suppressing hydrogen evolution reactions. Additionally, the BHEG adsorption layers can repel 39.3% of H₂O molecules at the Zn interface, creating a “water-deficient” inner Helmholtz plane and preventing Zn corrosion. Significantly, the N(CH₂)₃ groups in BHEG also inhibit polyiodide shuttle at the I₂ cathode, which exhibits high adsorption energies of −0.88, −0.41, and −0.39 eV for I⁻, I_2, and I₃⁻, respectively. Attributing to these benefits, the Zn–I₂ battery can achieve a high areal capacity of 2.99 mAh cm⁻² and an extended cycling life of 2,000 cycles, even at a high mass loading of I₂ cathode (≈21.5 mg cm⁻²).