Dual-function electrolyte additive enabling simultaneous electrode interface and coordination environment regulation for zinc-ion batteries

Despite advantages of low cost, high safety, and high capacity, aqueous zinc-ion batteries are facing challenges of zinc dendrite and side reactions. Herein, a low-cost and biocompatible electrolyte additive with dual-function is designed to simultaneously optimize the electrode interface and Zn2+ coordination environment. Due to the high hydrogen-bond donors and acceptors' properties, phytic acid (PA) is selected for electrolyte optimization. Both simulation and experimental results show that the PA additives can absorb on the electrode surface, covering the active sites for proton attack and guiding the uniform deposition of zinc. The absorbed PA is also conducive to the de-hydration of Zn [(H2O)6]2+ through hydrogen bonding interactions between PA and water. Additionally, PA has a strong affinity to Zn2+ and can compete with water molecules in the Zn [(H2O)6]2+, reducing the water molecules in the first hydration layer of Zn2+. The finite element simulation further illustrates a more uniform distribution of current density and zinc deposition with PA adsorption. Specifically, high Coulombic efficiency of 99.4% and long cycling stability of more than 1200 cycles are obtained with the PA additive at 1 mA cm-2 and 1 mAh cm-2 with the zinc foil of 100 mu m. When coupling with the I2/ active carbon cathode, the full cell with the PA additive delivers a high capacity of 110 mAh g-1 at 1 A g-1, and can stably cycle for more than 2500 cycles. This work provides a direction on seeking dual-function electrolyte additives with high hydrogen bonding do-nors/acceptors to inhibit Zn dendrite and parasitic reactions.

Automated summary

A low-cost and biocompatible electrolyte additive with dual-function is designed to optimize the electrode interface and Zn2+ coordination environment. The phytic acid additive can absorb on the electrode surface, cover the active sites for proton attack, and guide the uniform deposition of zinc. It also helps in the de-hydration of Zn [(H2O)6]2+ and reduces water molecules in the first hydration layer of Zn2+ through hydrogen bonding interactions.