Thickening and Homogenizing Aqueous Electrolyte towards Highly Efficient and Stable Zn Metal Batteries

Rechargeable Zn metal aqueous batteries featuring low cost, superior safety, and ultrahigh volumetric capacity are of great interest for large-scale applications. However, their practical implementation is hindered by poor reversibility and short cycling stability, which fundamentally result from the corrosion and the dendritic growth of the Zn metal anode in the aqueous electrolyte. Stabilization of Zn metal is therefore essential to achieve satisfactory performances. Here, we report a new electrolyte system containing a thickening agent (fumed silica) that can immobilize the water molecules and a homogenizing agent (fatty methyl ester ethoxylate) that assists in smoothing the Zn 2+ cations deposition, which effectively alleviates the water-induced corrosion reaction and suppresses the Zn dendrite formation. Zn/Zn symmetric cells in the new electrolyte, therefore, show extraordinary reversibility with a coulombic efficiency of 99.5% that is the highest among those of the reported symmetric cells and a long cycling stability of 1500 h. Furthermore, the Zn-MnO 2 full cell in this work exhibits equally excellent cycling stability with low capacity loss of 0.002% per cycle, which is superior to those of previously developed Zn metal batteries. This study offers a promising approach to stabilize Zn metal and enable high-performance Zn metal aqueous battery.