Synergistic Interfacial Regulation of Both Anode and Cathode via a Multifunctional Additive for Highly Stable Aqueous Zn–Mn Batteries

ABSTRACT Aqueous Zn–Mn batteries represent a promising technology for grid‐scale energy storage, yet their practical deployment is hindered by interfacial instability at both electrodes, including dendrite growth, hydrogen evolution reactions (HER), and corrosion at the anode and irreversible dissolution at the cathode. Herein, hypotaurine (HypTau) is introduced as a multifunctional electrolyte additive to achieve synergistic interfacial regulation on both sides, supported by comprehensive density functional theory (DFT) calculations and experimental analyses. On the Zn anode, HypTau preferentially adsorbs on the Zn surface, forming a water‐repellent electric double layer and an in situ‐constructed gradient organic–inorganic hybrid solid electrolyte interphase (SEI), while also serving as an effective pH buffer. These three components collectively suppress water‐induced side reactions, homogenize Zn 2 + flux, and lower the nucleation overpotential, enabling uniform Zn deposition. On the MnO 2 cathode, HypTau adsorption induces electron accumulation at the interface, thereby establishing a negatively charged environment which in turn facilitates Mn 2 + enrichment and promotes its re‐deposition during charging, thus significantly improving the reversibility of the two‐electron reaction. As a result, Zn||Zn symmetric cells achieve an extended cycling lifespan of 2155 h, and Zn||MnO 2 full cells without pre‐added Mn 2 + retain stable operation for over 5000 cycles.