A Rechargeable Neutral Hybrid Zn‐Air/MnO₂ Battery with High Energy Efficiency

Abstract Neutral rechargeable Zn‐air batteries (ZABs) offer high energy density, safety, and cost‐effectiveness. However, energy efficiency is limited by sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, along with the formation of low‐conductivity discharge products. Here, a high‐efficiency neutral hybrid Zn‐air/MnO₂ battery (ZAMB) is introduced, where MnO₂ is in situ electrodeposited on the air cathode in a ZnSO₄‐MnSO₄ electrolyte. The electrodeposited MnO₂ acts as the active material for the Zn‐MnO₂ battery and as a dynamically formed catalyst for the ORR/OER processes. In situ pH and X‐ray diffraction (XRD) analyses verify its effect in promoting the reversible formation and decomposition of low‐conductivity discharge products. The hybrid ZAMB achieves an energy efficiency of 68%, a significant increase from 38% in conventional ZABs, and exhibits better cycling stability, operating reliably over 100 h at a current density of 1 mA cm⁻² and up to 300 h at 0.1 mA cm⁻². A rechargeable pouch‐type ZAMB delivering a fixed capacity of 1 Ah demonstrates the practical potential of this hybrid design. This work integrates multiple electrochemical reactions in a single hybrid battery, improving energy efficiency, longevity, and the performance of metal‐air batteries with low‐conductivity discharge products.