<p>Lithium (Li)-metal anode undergoes large volume expansion during repeated charging and discharging processes, which leads to serious damage to the structural integrity of the Li-metal surface, uneven current density distribution at the interface, and the generation of uncontrollable Li dendrites or inactive Li. Herein, we have designed an easily scalable, low-cost iodine-containing electrolyte engineering for releasing inactive Li and constructing high-integrity interfacial Li-metal anodes. X-ray photoelectron spectroscopy (XPS) verifies that the LiI is involved in the composition of solid–electrolyte interphase (SEI) in the battery after activation. Furthermore, density functional theory (DFT) calculations indicate that the LiI has higher electronic insulation and ionic conductivity compared with the conventional inorganic component of SEI, which not only inhibits the inhomogeneous nucleation of Li⁺, but also improves the interfacial migration kinetics. Benefiting from this elaborated iodine-containing electrolyte, an ultra-long-cycle number of 1370 cycles at a current density of 5&#xa0;mA&#xa0;cm⁻² were achieved in Li symmetric battery, and the structural integrity of the Li anode surface was still maintained. In addition, to verify the feasibility of this strategy for practical applications, the Li-metal full batteries assembled with highly loaded LiFePO₄ (17.4&#xa0;mg&#xa0;cm⁻², 3.0&#xa0;mAh&#xa0;cm⁻²) cathode also demonstrated satisfactory long cycle stability and capacity retention.</p>