Comparative study of the performance of α-MnO2 and amorphous manganese dioxide air electrodes for zinc-air batteries

In order to determine the optimal crystalline form of manganese-based catalysts for zinc-air battery cathodes, in this paper nano-α-MnO₂ and amorphous manganese dioxide (AMO) materials were successfully synthesised by hydrothermal and liquid-phase co-precipitation methods, respectively. The results show that the spherical AMO material has larger specific surface area and more mesopores than the rod-like α-MnO₂. Moreover, AMO has abundant structural defects and short-range ordered atomic arrangements that can enhance the ion diffusion kinetics and improve the catalytic performance of the materials. Through electrochemical tests, it is found that the AMO materials have better catalytic properties compared to α-MnO₂. At a current of 10 mA/cm², its discharge-specific capacity reached 575.2 mAh/g, which is 11.1% higher than that of 517.8 mAh/g for α-MnO₂. And AMO have higher peak power density and smaller charge/discharge voltage gaps. In the long-cycle test, the initial round-trip efficiency of the electrode prepared of AMO is also better than that of α-MnO₂. However, when the AMO electrodes are charged and discharged for a long time, part of the AMO will be converted to α-MnO₂, which lead to a gradual decrease in the cycling stability of the AMO electrodes. Therefore, this paper concludes that AMO materials are superior to α-MnO₂ as catalysts for zinc-air batteries.