High-Energy and Long-Lived Zn-MnO₂ Battery Enabled by a Hydrophobic-Ion-Conducting Membrane.

Abstract

Alkaline Zn-MnO₂ batteries feature high security, low cost, and environmental friendliness while suffering from severe electrochemical irreversibility for both the Zn anode and MnO₂ cathode. Although neutral electrolytes are supposed to improve the reversibility of the Zn anode, the MnO₂ cathode indeed experiences a capacity degradation caused by the Jahn-Teller effect of the Mn³⁺ ion, thus shortening the lifespan of the neutral Zn-MnO₂ batteries. Theoretically, the MnO₂ cathode undergoes a highly reversible two-electron redox reaction of the MnO₂/Mn²⁺ couple in strongly acidic electrolytes. However, acidic electrolytes would inevitably accelerate the corrosion of the Zn anode, making long-lived acidic Zn-MnO₂ batteries impossible. Herein, to overcome the challenges faced by Zn-MnO₂ batteries, we propose a hybrid Zn-MnO₂ battery (HZMB) by coupling the neutral Zn anode with the acidic MnO₂ 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 MnO₂ 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-MnO₂ batteries in terms of voltage and cycle life.