High-Energy Density Aqueous Zinc-Iodine Batteries with Ultra-long Cycle Life Enabled by the ZnI2 Additive

Aqueous zinc-iodine batteries, featuring high energy density, safety, and cost-effectiveness, have been regarded as a promising energy storage system. Nevertheless, poor cycling stability and dissolution of iodine/polyiodide have greatly limited the development of zinc-iodine batteries. Here, iodine encapsulated by hierarchical porous carbon is employed as a positive material to assemble high-performance zinc-iodine batteries. Meanwhile, the utilization of the ZnI2 additive in the electrolyte can enhance the capacity and cycling stability of as-assembled devices because the existence of polyiodide (I-3(-) and I-5(-)) can effectively inhibit the dissolution of iodine. Thanks to the high conductivity and interconnected structure of the prepared carbon material, the asassembled zinc-iodine batteries deliver an excellent specific capacity of 360.6 mA h g(-1) at 0.5 C, a superb durability (similar to 98.4% retention of the initial capacity at a high density of 50 C after 35,000 cycles), and an ultra-high energy/power density of 422.6 W h kg(-1)/21.6 kW kg(-1). Significantly, the mechanism of the constructed device was investigated by ex-situ Raman and ex-situ X-ray diffraction. Besides, when coupling carbon@I-2 electrodes with the hydrogel electrolyte to assemble quasi-solid-state zinc-iodine batteries, the as-built device can well service for an electronic clock.

Automated summary

The study focuses on improving the cycling stability and capacity of zinc-iodine batteries using hierarchical porous carbon encapsulated iodine and ZnI2 additive in the electrolyte, achieving high performance in high-efficiency zinc-iodine batteries. Through ex-situ investigation, the working mechanism of the device was revealed.