PEG-water Electrolyte for High-performance Zinc iIodine Dual-ion Batteries

Xiaofeng QU, Guangdong University of Technology, Guangzhou 510006, China;
Yuting TANG, Guangdong University of Technology, Guangzhou 510006, China;
Xincheng HE, Guangdong University of Technology, Guangzhou 510006, China;
Jiasheng ZhOU, Guangdong University of Technology, Guangzhou 510006, China;
Ziheng TANG, Guangdong University of Technology, Guangzhou 510006, China;
Wenhua FENG, Office of the CPC Nie Rong County Committee, Naqu, 853500,China
Jun LIU, Guangdong University of Technology, Guangzhou 510006, China;

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 are added in zinc-ion aqueous electrolyte. PEG400 form complexation with iodine to reduce the dissolution of iodine, therefore alleviating the formation of soluble triiodide (I3-) from iodine and iodide ions. Finally, this electrolyte was assembled into the battery with double carbon cloth current collectors, double separators and zinc anode. At 1 mA·cm-2 current density, the first discharge capacity reaches 1.62 mAh·cm-2, and the Coulomb efficiency is 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 Coulomb efficiency still remains 98%, and the rate of capacity retention was 58.33% after 1,200 cycles.