Abstract
In order to determine the optimal crystalline form of manganese-based catalysts for zinc-air battery cathodes, this paper successfully synthesised nano α-MnO2 and amorphous manganese dioxide (AMO) materials by hydrothermal and liquid-phase co-precipitation methods, respectively. The results showed that the spherical AMO material had larger specific surface area and more mesopores than the rod-like α-MnO2. Moreover, AMO have 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 was 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 was 11.1 % higher than that of 517.8 mAh/g for α-MnO2. In the long-cycle test, the initial round-trip efficiency of the electrode prepared of AMO was also better than that of α-MnO2. However, when the AMO electrodes were charged and discharged for a long time, part of the AMO would be converted to α-MnO2, which led 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.