High-Energy and Long-Lived Zn-MnO 2 Battery Enabled by a Hydrophobic-Ion-Conducting Membrane.

Alkaline Zn-MnO ₂ batteries feature high security, low cost, and environmental friendliness while suffering from severe electrochemical irreversibility for both the Zn anode and MnO ₂ cathode. Although neutral electrolytes are supposed to improve the reversibility of the Zn anode, the MnO ₂ cathode indeed experiences a capacity degradation caused by the Jahn-Teller effect of the Mn ³⁺ ion, thus shortening the lifespan of the neutral Zn-MnO ₂ batteries. Theoretically, the MnO ₂ cathode undergoes a highly reversible two-electron redox reaction of the MnO ₂ /Mn ²⁺ couple in strongly acidic electrolytes. However, acidic electrolytes would inevitably accelerate the corrosion of the Zn anode, making long-lived acidic Zn-MnO ₂ batteries impossible. Herein, to overcome the challenges faced by Zn-MnO ₂ batteries, we propose a hybrid Zn-MnO ₂ battery (HZMB) by coupling the neutral Zn anode with the acidic MnO ₂ cathode, wherein the neutral anode and acidic cathode are separated by a proton-shuttle-shielding and hydrophobic-ion-conducting membrane. Benefiting from the optimized reaction conditions for both the MnO ₂ cathode and Zn anode as well as the well-designed membrane, the HZMB exhibits a high working voltage of 2.05 V and a long lifespan of 2275 h (2000 cycles), breaking through the limitations of Zn-MnO ₂ batteries in terms of voltage and cycle life.