Zn-I2 batteries have emerged as a compelling electrochemical energy storage platform, benefiting from their excellent theoretical capacity, inherent safety, and low cost. Nevertheless, their development, especially on the separator, is impeded by the severe shuttle of polyiodides and sluggish reaction kinetics. To address these challenges, this work demonstrates the design of Gadolinium (Gd) and Europium (Eu) co-doped cerium oxide (CeO2) nanoparticles as a functional separa