Electrolyte additive for improving anodic stability in aqueous Zn-ion batteries

Abstract

The development of durable aqueous Zn-ion batteries (ZIBs) faces significant challenges due to severe parasitic reactions as well as the uncontrolled generation of dendrites on the anode. In this study, a stable dendrite-free Zn anode is obtained by introducing trace amounts (30 mM) of propylene glycol methyl ether acetate (PGMEA) as an electrolyte additive. The results reveal that PGMEA can effectively inhibit water-related side reactions, likely by coordinating with water molecules and regulating the solvation sheath of Zn²⁺. Furthermore, PGMEA, which contain polar oxygen groups, can adsorb onto the Zn electrode surface, forming a protective layer that discourages Zn corrosion and the formation of irreversible side products such as Zn₄SO₄(OH)₆·5H₂O. This adsorbed PGMEA also increases the nucleation overpotential, which increases the nucleation sites on the electrode surface and discourages the lateral diffusion of Zn atoms during deposition, leading to planar growth over dendrite formation. Consequently, Zn‖Zn cells were able to achieve an exceptionally long lifespan of 2980 h (1 mA cm⁻², 1 mAh cm⁻²), while Zn‖V₂O₅ full cells exhibited enhanced rate capability and an improved discharge capacity of 133 mAh g⁻¹ over 1000 cycles at 2 A g⁻¹. The Zn²⁺ transference number was also observed to increase from 0.46 to 0.79 with the addition of PGMEA.