Reversible Protonated Electrolyte Additive Enabling Dendrites-Free Zn Metal Anode with High Depth of Discharge

Aqueous zinc ion batteries (AZIBs) have stimulated extensive attention due to their environmental friendliness and low cost. Unfortunately, the inevitable dendrite growth and corrosion on the zinc (Zn) anode severely hinder the practical application of AZIBs. Herein, an amino acid containing an imidazole group is introduced as an effective additive to address these issues. The dynamic conversion of amino acid and protonated amino acid creates a pH buffer function that regulates solution pH in real time, inhibits hydrogen evolution reaction (HER), and eliminates notorious by-products. In addition, the protonated amino acid is preferentially adsorbed on the Zn anode, preventing contact of the active water with the Zn surface and promoting homogeneous Zn deposition. Thus, the amino acid-based electrolyte promotes dendrite free plating/stripping with a Coulombic efficiency up to 99.67% and cycle lifetime of 2600 h. In particular, a depth of discharge of up to 87% can be achieved with an ultra-high areal capacity of 24 mAh cm-2. The developed Zn||CVO full cell also exhibits better electrochemical performance than that without additives. This work provides an effective and convenient approach for safe and efficient Zn-ion batteries. L-histidine (LH) is reported as an additive to stabilize the hydrogen ion environment in electrolyte, and the reversible conversion of LH to protonated LH can effectively inhibit side reaction and induce uniform deposition of zinc. The Zn||Zn symmetric cell exhibits a 270 h lifetime with a high depth of discharge (DOD) of 80%, indicating a highly reversible plating/stripping process. image