Dual-function additive enables a self-regulatory mechanism to balance cathode–anode interface demands in Zn‖MnO2 batteries

The poor reversibility of the zinc (Zn) anodes and the irreversible deposition/dissolution of Mn²⁺/MnO₂ significantly impede the commercialization of Zn-Mn aqueous batteries (ZMABs). In reducing the difference between the desired interfacial reaction environments of the cathode and anode, we found that they face the same problem of interference-the generation of irreversible corrosion products. Herein, we have introduced a novel self-regulatory mechanism. This mechanism involves the addition of sodium dihydrogen phosphate, which shifts from passive protection to active regulation. It effectively captures OH^- ions, prevents corrosion product formation, and facilitates the in situ generation of a solid electrolyte interface (SEI) film. This modification also homogenizes Zn ion flow and improves the reversibility of Zn plating and stripping. Furthermore, a stable and slightly acidic environment has been established to stabilize the pH at the cathodic interface, mitigate corrosion product formation, and enhance the reversible deposition and dissolution of Mn²⁺/MnO₂. With the optimal electrolyte, Zn‖Zn symmetric cells demonstrate stable operation for over 3000 hours at 1 mA cm^-2, 1 mA h cm^-2. Additionally, the Zn‖Cu cells maintain high reversibility after 1000 cycles, achieving an average coulombic efficiency (CE) of 99.76%. The assembled Zn‖MnO₂ full cells exhibit exceptional cycling stability and rate performance. This work adopts the approach of seeking common ground and emphasizing the balance of cathode and anode interfacial requirements, which represents a new and significant insight for design of ZMABs with high reversibility and high cyclability.