Optimizing electrolyte systems for stable and low-temperature zinc-ion batteries via efficient coordinator

Abstract

Aqueous zinc-ion battery suffers poor cycling stability due to uneven Zn2+ deposition and serious dendrite growth. To effectively protect the Zn metal anode, diglyme (G2) is added as the co-solvent. Adding G2 can reconstruct the Zn2+ solvation structure and reduce the water molecule content of [Zn(H2O)6]2+ sheath. Theoretical calculations confirm that by adding G2, the triflate group OTF− ion shows greater interaction with Zn, and the water molecules from the [Zn(H2O)6]2+ solvation structure are replaced by OTF− ions. Benefitted from this, an organic-inorganic SEI layer is formed on the Zn anode, which isolates the Zn anode from the bulk electrolyte, and allows/suppresses Zn2+ diffusion. As well, Zn corrosion and side reactions are inhibited in this system. This co-solvent electrolyte system has a high Coulombic efficiency of 99.7%. A long cycling life of 1000 cycles with capacity retention of 80% is demonstrated by Zn//iodine (I2) - Activated Carbon (AC) full cell at room temperature. Even under a low-temperature condition (−18 °C), Zn//I2 - AC full cell shows a long lifespan of 1000 cycles with capacity retention of 65%. This work demonstrates a new direction and unparalleled insight into electrolyte engineering with solvation structure regeneration and SEI player formation for aqueous zinc-ion batteries.