As one of the most appealing energy storage technologies, aqueous zinc-iodine batteries still suffer severe problems such as low energy density, slow iodine conversion kinetics, and polyiodide shuttle. This review summarizes the recent development of Zn─I2 batteries with a focus on the electrochemistry of iodine conversion and the underlying working mechanism. Starting from the fundamentals of Zn─I2 batteries, the electrochemistry of iodine conversion and zinc anode, as well as the scientific problems existing in Zn─I2 batteries are introduced. The concrete strategies dealing with cathode, anode, electrolyte, and separator challenges confronting Zn─I2 batteries are elaborated as well. To deepen the understanding of the electrochemistry of Zn─I2 batteries, the recent important findings of the underlying working mechanism of different Zn─I2 batteries are summarized in detail. Finally, some guidelines and directions for Zn─I2 batteries are also provided. This review is expected to deepen the understanding of Zn─I2 battery electrochemistry and promote their practical applications in the future.