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

Abstract Aqueous zinc–iodine (Zn–I 2 ) 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 I 2 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(CH 2 ) 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 H 2 O molecules at the Zn interface, creating a “water‐deficient” inner Helmholtz plane and preventing Zn corrosion. Significantly, the N(CH 2 ) 3 groups in BHEG also inhibit polyiodide shuttle at the I 2 cathode, which exhibits high adsorption energies of −0.88, −0.41, and −0.39 eV for I − , I 2, and I 3 − , respectively. Attributing to these benefits, the Zn–I 2 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 I 2 cathode (≈21.5 mg cm −2 ).