Abstract Li−I2 batteries have attracted much interest due to their high capacity, exceptional rate performance, and low cost. Even so, the problems of unstable Li anode/electrolyte interface and severe polyiodide shuttle in Li−I2 batteries need to be tackled. Herein, the interfacial reactions on the Li anode and I2 cathode have been effectively optimized by employing a well‐designed gel polymer electrolyte strengthened by cross‐linked Ti–O/Si–O (GPETS). The interpenetrating network‐reinforced GPETS with high ionic conductivity (1.88 × 10−3 S cm−1 at 25°C) and high mechanical strength endows uniform Li deposition/stripping over 1800 h (at 1.0 mA cm−2, with a plating capacity of 3.0 mAh cm−2). Moreover, the GPETS abundant in surface hydroxyls is capable of capturing soluble polyiodides at the interface and accelerating their conversion kinetics, thus synergistically mitigating the shuttle effect. Benefiting from these properties, the use of GPETS results in a high capacity of 207 mAh g−1 (1 C) and an ultra‐low fading rate of 0.013% per cycle over 2000 cycles (5 C). The current study provides new insights into advanced electrolytes for Li−I2 batteries.
