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

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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.