In Situ Synthesis of Cathode Materials for Aqueous High-Rate and Durable Zn–I₂ Batteries

Rechargeable aqueous zinc–iodine batteries are considered as one of strong contenders for next-generation energy storage systems by virtue of their low cost and high safety. However, the shuttle effect of highly soluble I3– in zinc–iodine batteries leads to a rapid decrease in capacity and Coulomb efficiency during cycling, which seriously hinders their further development and application. Here, we developed an in situ synthesis of an aqueous fast-charging and ultrastable Zn–I2 battery cathode materials composed of mesoporous carbon and I2. Compounding I2 with highly conductive carbon is an effective method to facilitate electron and ion transport and confine polyiodides/I– conversion reaction inside pores, thereby eliminating polyiodides shuttle effect, which greatly improves cycling stability of Zn–I2 batteries. The developed Zn–I2 battery provides a specific capacity of 90 mAh g–1 at 5 A g–1, excellent multiplicative performance, and retains a capacity retention of 80.6% over an ultralong period of 39 000 cycles at 10 A g–1, superior to previously reported Zn–I2 batteries. Furthermore, Zn–I2 pouch cell retained 89% capacity retention over 1000 cycles at 0.5 A g–1. This work undoubtedly sets a precedent for ultralong cycle life Zn–I2 battery cathode materials and provides an important solution and pathway for the assembly of I2-based materials suitable for high-performance aqueous energy technologies.