Advanced Zn-I Battery with Excellent Cycling Stability and Good Rate Performance by a Multifunctional Iodine Host.

The rechargeable zinc-iodine (Zn-I) battery is a promising energy-storage system due to its low cost and good security, but the practical use of the battery is largely constrained by the shuttle effect and high dissolvability of iodides. Here a multifunctional iodine host, constructed with nitrogen-doped porous carbon nanocages (NCCs) by the polymerization carbonization activation method, is exploited to improve the electrochemical performance and lifespan of the Zn-I battery, achieving a high specific capacity of 259 mAh g, a good rate performance (maintaining 50.6% expanding 50 times), and a high cycle stability (retention of 100% after 1000 cycles). On the basis of the experimental results and theoretical calculations, NCCs via the introduction of N doping and nanosized porous structure can simultaneously provide rich and robust anchoring and catalytic sites to carry out the electrostatic adsorption of iodides and facilitate the reversible conversion between iodine and iodides. This work shows a novel and efficient strategy to develop high-performance and long-life Zn-I batteries.