Manipulating the Water‐Deficient Inner Helmholtz Plane toward Highly Reversible Zinc Batteries

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) are promising for large–scale energy storage applications. However, their practical application is hampered by parasitic reactions and dendrite formation on the zinc anode, issues that stem from the activity of H ₂ O molecules within the inner Helmholtz plane (IHP). Herein, a molecular‐scale tailoring of the IHP is achieved by introducing serinol (SN) as a dual‐functional electrolyte additive. SN simultaneously modulates the Zn ²⁺ solvation structure and preferentially adsorbs on the Zn surface, collaboratively forging a water‐deficient interfacial environment. This tailored IHP effectively suppresses water activity and homogenizes Zn ²⁺ flux, as validated by experimental and theoretical evidence, which confirms the reconstruction of the hydrogen‐bond network and the desolvation dynamics. Consequently, the engineered electrolyte enables exceptional cycling stability: a Zn||Zn symmetric cell achieves a lifespan of 5000 h at 1 mA cm ⁻² and 1 mA h cm ⁻² , and a Zn||CVNO full cell retains high capacity at 1 Ag ⁻¹ . This work demonstrates that precise IHP engineering via functional additives is a potent and generalizable strategy for stabilizing metal anodes in aqueous batteries.