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Aqueous zinc–chlorine battery with high discharge voltage and attractive theoretical energy density is expected to become an important technology for large‐scale energy storage. However, the practical application of Zn–Cl2 batteries has been restricted due to the Cl2 cathode with sluggish kinetics and low Coulombic efficiency (CE). Here, an aqueous Zn–Cl2 battery using an inexpensive and effective MnO2 redox adsorbent (referred to Zn‐Cl2@MnO2 battery) to modulate the electrochemical performance of the Cl2 cathode is developed. Density functional theory calculations reveal that the existence of the intermediate state Clads free radical catalyzed by MnO2 on the Cl2 cathode contributes to the charge storage capacity, which is the key to modulate the electrode and improve the electrochemical performance. Further analysis of the Cl2 cathode kinetics discloses the adsorption and catalytic roles of the MnO2 redox adsorbent. The Zn–Cl2@MnO2 battery displays an enhanced discharge voltage of 2.0 V at a current density of 2.5 mA cm−2, and stable 1000 cycles with an average CE of 91.6%, much superior to the conventional Zn–Cl2 battery with an average CE of only 66.8%. The regulation strategy to the Cl2 cathode provides opportunities for the future development of aqueous Zn‐Cl2 batteries. [ABSTRACT FROM AUTHOR]

Mg batteries utilizing divalent Mg2+ as charge carriers have been attracting significant attention for energy storage owing to their uniqueness in terms of low cost, high safety, and high energy density. However, the short cycling life arising from the accumulation of a passivation layer on the Mg anode prohibits their further development. Here, a new strategy to suppress the accumulation of the passivation layer is presented, thus stabilizing the Mg anode by constructing a robust interfacial layer using organic solvent‐in‐water electrolytes. The organic solvents decompose on the Mg anode to form a MgO, polyether Mg enriched organic‐inorganic hybrid interfacial layer, preventing free water attack to the Mg anode. In addition, the organic solvent forms an H‐bond with H2O to suppress the water activity and therefore protecting the Mg anode. As an illustration to benefits of the solvent‐in‐water electrolytes, a Mg‐MnO2 battery that is coupled by a MnO2 cathode in Mn2+/MnO2 chemistry with the Mg anode is developed. The Mg‐MnO2 battery exhibits a well‐maintained discharge plateau at ≈2.5 V and a discharging capacity of ≈500 mAh g−1 over 1000 cycles. This result highlights the feasibility to stabilize the Mg anode by interface engineering through the solvent‐in‐water electrolyte design. [ABSTRACT FROM AUTHOR]