No abstract

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.

The side reaction and dendrite of a zinc anode in an aqueous electrolyte represent a huge obstacle for the development of rechargeable aqueous Zn batteries. An electrolyte with confined water is recognized to fundamentally stabilize the zinc anode. This work proposes acetamide/zinc perchlorate hexahydrate (AA/ZPH) ionic liquid (IL)polyacrylamide (PAM) polymer electrolytes, here defined as IL-PAM. The novel Zn 2+ -conducting IL is able to accommodate trace water and can achieve both high conductivity (15.02 mS cm −1 ) and alleviation of side reactions (>90% reduction). Cross-linked PAM acts as the threedimensional framework to suppress dendrites and obtain flexibility. As a result, the Zn anode with IL-PAM can cycle stably over 2000 h with a record highest cumulative capacity of 3000 mAh cm −2 and well-preserved morphology. Based on IL-PAM, the flexible LFP|Zn hybrid batteries can be successfully assembled and operate normally in series and parallel conditions. Moreover, the low volatility of IL and binding forces exerted by the PAM network endues IL-PAM with an antidehydration property. In a 50 °C unsealed environment, the weight loss of IL-PAM is about two-fifths of PAM hydrogel and an aqueous electrolyte, and the corresponding hybrid battery with IL-PAM can also prolong a 4 times longer lifespan.