In Situ Synthesis of Cathode Materials for Aqueous High-Rate and Durable Zn-I-2 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 I-3(-) 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-I-2 battery cathode materials composed of mesoporous carbon and I-2. Compounding I-2 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-I-2 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-I-2 batteries. Furthermore, Zn-I-2 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-I-2 battery cathode materials and provides an important solution and pathway for the assembly of I-2 -based materials suitable for high-performance aqueous energy technologies.