This study introduces a bifunctional binder, LA133 (a polyacrylonitrile copolymer), designed to address the shuttle effect in aqueous zinc–iodine (Zn–I2) batteries. The binder effectively suppresses polyiodide shuttling by strongly bonding to iodine species through its amide and carboxyl groups, leading to reduced byproducts, slower hydrogen evolution, and less Zn dendrite formation. The Zn–I2 battery with LA133 binder exhibits high specific capacity (202.8 mAh g−1), high iodine utilization efficiency (96.1%), and a long cycling lifespan (2700 cycles). At a high mass loading of 7.82 mg cm−2, the battery retains 83.3% of its initial capacity after 1000 cycles, with a specific capacity of 71.2 mAh g−1 based on total cathode slurry mass. The strategy opens a new avenue for improving Zn–I2 battery performance by addressing the shuttle problem through functional binder design.This study introduces a bifunctional binder, LA133 (a polyacrylonitrile copolymer), designed to address the shuttle effect in aqueous zinc–iodine (Zn–I2) batteries. The binder effectively suppresses polyiodide shuttling by strongly bonding to iodine species through its amide and carboxyl groups, leading to reduced byproducts, slower hydrogen evolution, and less Zn dendrite formation. The Zn–I2 battery with LA133 binder exhibits high specific capacity (202.8 mAh g−1), high iodine utilization efficiency (96.1%), and a long cycling lifespan (2700 cycles). At a high mass loading of 7.82 mg cm−2, the battery retains 83.3% of its initial capacity after 1000 cycles, with a specific capacity of 71.2 mAh g−1 based on total cathode slurry mass. The strategy opens a new avenue for improving Zn–I2 battery performance by addressing the shuttle problem through functional binder design.