Turning the Byproduct Zn₄(OH)₆SO₄·xH₂O into a Uniform Solid Electrolyte Interphase to Stabilize Aqueous Zn Anode

Aqueous Zn anodes suffer from continuous side reactions and severe dendrite growth upon Zn plating and stripping, mainly due to the lack of an efficient protective layer. Herein, we report a facile approach to turn the byproduct Zn4(OH)6SO4·xH2O (ZHS) into a uniform solid electrolyte interphase (SEI) by simply introducing a small amount Zn(OH)2 into the ZnSO4 electrolyte. It is revealed that the uniform ZHS-based SEI possesses low electronic conductivity, high Zn2+ ion conductivity, and high zincophobicity, which could significantly restrain the dendrite growth and side reactions. Specifically, the designed electrolyte (1.98 M ZnSO4 + 0.02 M Zn(OH)2) enables the Zn∥Zn symmetric cell to deliver a long lifetime of 1190 h under 2 mA cm–2 with 2 mAh cm–2, and the Zn∥Ti asymmetric cell to achieve a high average Coulombic efficiency of 99.2%. This control of byproducts to construct the SEI proposes new insights and design ideas for stabilizing aqueous metal anodes.