High-Voltage and Ultrastable Aqueous Zinc–Iodine Battery Enabled by N-Doped Carbon Materials: Revealing the Contributions of Nitrogen Configurations

The rechargeable aqueous zinc–iodine (Zn–I2) battery has emerged as a promising electrochemical energy storage technology. However, poor cycling stability caused by the dissolution of iodine species into the electrolyte limited its practical application. Herein, we report a nitrogen-doped porous carbon (NPC) material in gram scales. Performed as an iodine host in the Zn–I2 battery, the NPC shows a high specific capacity (345.3 mAh g–1 at 0.2 C), superior rate capability (53.2% capacity retention at 10 C), and remarkable cycling stability (10 000 cycles at 10 C with a capacity retention of 80.9%). More importantly, DFT computations reveal that the graphitic-N (N-Q) exhibits the strongest adsorption of iodine; however, pyridinic-N (N-6) shows the weakest adsorption of iodine. Moreover, the N-6/N-Q ratio is an essential parameter that significantly determined the electrochemical performance of Zn–I2 batteries. Therefore, the improved long-term cycling stability and rate capability of the as-designed Zn–I2 battery are attributable to the decrease of the N-6/N-Q ratio. This work is of great significance for devolving highly reversible Zn–I2 batteries.