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

This work presents a hybrid Zn-air/MnO₂ battery that combines a reversible insertion type Zn-MnO₂ battery with a Zn-air battery, resulting in significant improvements in energy efficiency and cycling stability. By utilizing in situ electrodeposited MnO₂ as both the active material and a bifunctional ORR/OER catalyst, the hybrid design effectively regulates low-conductivity discharge products and their decomposition, improving overall performance.

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.