Research On Cathode Materials Of Aluminum-air Battery In Alkaline Medium

The oxygen electrode catalyst is the one of key problem of Aluminium-air battery. Additionally, the structure of air electrode has a great influence on the electrochemical performance of Aluminium-air battery. In this article, the preparation of the catalyst, air electrode were studied and explored systematically. The manganese oxide catalyst Mn3O4was prepared by the pyrolytic method and the compound oxide catalyst was prepared by the high-energy ball-milling method as well. XRD and SEM were employed to characterize the prepared catalysts. The polarization curves, impedence spectroscopy methods and the galvanostatic discharge curves were used to study the electrocatalytic performances of the prepared catalyst in6mol/L KOH solution. The results are shown as follows:(1)Catalyst layer should be based on activated carbon/acetylene black as its carrier. Through the optimization of the preparation process of air electrode we could find that:the optimal parameter of thermal treatment for the acetylene black was330℃3h; the optimal parameter of pyrolysis for manganous nitrate was340℃2h;the best content of the catalyst was20%;the optimum mass ratio of activated carbon/acetylene black in the catalyst layer was4:l;the most suitable catalyst layer thickness was0.25mm;nichel foam exerts better electrochemical performance than copper net.(2)In the doping experiment of manganite which was prepared by the pyrolytic method, the analysis of cathodic polarization method demonstrated that the air electrode expressed the smallest polarization when the stoichiometric ratio of Mn:La:Co was1:0.4:0.6. The result of galvanostatic discharge method indicated that the discharge plateau of the electrode [Mn:La:Co=1:0.4:0.6] was much higher than the electrode of MnOX at current densities of100and200mA·cm-2. Furthermore, the composite catalyst could boost the stability of the electrode for ORR at large current density. The investigation of AC impedance spectra revealed that the doping of La and Co could decrease the charge-transfer resistance and oxygen diffusion resistance. The discharge results showed that the lanthanum oxide and cobalt oxide could significantly enhance the Al-air battery’s operating voltage.(3)In the experiment of the preparation of mixed oxide catalyst which was synthesized by the high-energy ball-milling technique, the analysis of cathodic polarization method demonstrated that the electrochemical property of binary catalyst was better than separate catalyst, and that EMD+CaO+La2O3catalyst exerted the best electrochemical property. The result of galvanostatic discharge method indicated that the discharge plateau of the electrode EMD+CaO+La2O3was much higher than the electrode of EMD at the current densities of100and200mA·cm-2. Furthermore, the mixed catalyst could boost the stability of the electrode for ORR at large current density. The investigation of AC impedance spectra revealed that the addition of calcium oxide and lanthanum oxide could decrease the charge-transfer resistance and oxygen diffusion resistance. The discharge results showed that the addition of lanthanum oxide and calcium oxide could significantly enhance the Al-air battery’ s operating voltage.