Polar small molecular electrolyte additive for stabilizing Zn anode

Zinc (Zn) metal is considered as one of the ideal anode materials for aqueous metal batteries on account of its advantages of high safety, low cost, high theoretical capacity and environmental friendliness. However, the rapid development of Zn metal devices is hindered by unpredictable problems, such as dendritic growth, hydrogen evolution, and corrosion side-reactions of Zn metal. To address these difficulties, the low-cost erythritol (Et) is used as an additive in typical ZnSO4 electrolyte not only to homogenize the local electric field by adjusting the solvate structure of hydrated Zn2+, but also to alter the hydrogen evolution active site and overpotential through the low unoccupied molecular orbital energy of Et. As a result, the Zn||Zn symmetric cell using Et additive display an exceedingly prolonged cycle life of about 2000 h at 0.23 mA cm−2/0.23 mAh cm−2, significantly higher than that of using pure ZnSO4 electrolyte of 220 h, meanwhile, the Coulombic efficiency of the Zn||Cu battery using Et additive is as high as 99% under a high cumulative plated capacity of 2.0 mAh cm−2. Besides, at current densities of 2.0 mA cm−2 and 5.0 A/g, the full batteries assembled using MnO2 and V2O5 as cathodes can tolerate 2000 and 1000 cycles, respectively, and their capacity retention rates are higher than those without additives. This work indicates that the use of polar small molecular additives to regulate ion deposition is an effective strategy for stabilizing Zn anode and shed novel perspective for the development of long-life, high-stability, environment-friendly, and low-cost aqueous zinc ion batteries.