Deeply Discharged, Quiescently Stable, and Long‐Life Zn Anode by Spontaneous SEI Formation

Zn ion batteries (ZIBs) are a promising candidate in safe and low-cost large-scale energy storage applications. However, significantly deteriorated cycling stability of Zn anode in high depth of charge or after long-term quiescence impedes the practical application of ZIBs. Aiming at the above issue, a spontaneous solid electrolyte interphase (SEI) formation of Zn₄(OH)₆SO₄·xH₂O (ZHS) on Zn powder is achieved in pure ZnSO₄ electrolyte by facile and rational interface design. The stable and ultrathin ZHS SEI plays a crucial part in insulating water molecules and conducting Zn²⁺ ions, intrinsically suppressing the severe hydrogen evolution and dendrite formation on the Zn powder anode. The ZHS-Zn anode delivers a stable cycling at a high DOD of 50% for over 500 h, as well as a lifespan of over 200 h after 40-days of resting at a DOD of 25%. Benefiting from the high utilization of Zn anode, the energy density of the Zn-Mn_xV₂O₅ full cell is up to 118 Wh Kg^-1. This facile method can fabricate the ZHS-Zn anode as long as 1 m, revealing its feasibility in large-scale production and commercialization.