关键词: 锌碘电池, PEG400, 双离子电池, 络合, 高电流密度

Abstract:

Thanks to abundant resource and rapid redox reaction kinetics, iodine is regarded as promising positive materials in the batteries. However, the shuttling effect due to the high solubility of iodine in the electrolyte makes the performance of battery poor. In this paper, polyethylene glycol (PEG400) and potassium iodide were added into zinc-ion aqueous electrolyte. PEG400 could complex with iodine to reduce the dissolution of iodine, therefore alleviating the formation of soluble triiodide (I₃^-) from iodine and iodide ions. Furthermore, this electrolyte was used in the battery with double carbon cloths as the current collectors, double separators and zinc anode. At the current density of 1 mA·cm^-2, the first discharge capacity reached 1.62 mAh·cm^-2, and the coulombic efficiency was around 93%. Iodine involved in the electrochemical redox reaction is calculated to account for 47.52% of the total mass of iodine in this electrolyte. At high current density of 7 mA·cm^-2, its coulombic efficiency still remained 98%, and the rate of capacity retention was 58.33% after 1,200 cycles.

Key words: Zinc iodine battery, PEG400, Dual-ion batteries, Complexation, High current density