Research On Al-Mg-Sn-Ga Alloy Anode Materials For Aluminum-air Batteries

In this thesis,Al-0.08Sn-0.08Ga-xMg（x=0,0.5,1.0,1.5,2.0）anode alloys were prepared with high-purity aluminum and elements Sn,Ga and Mg according to the alloying method.The hydrogen evolution rate of aluminum alloy anode materials was measured by drainage method.The morphology of the anode alloy was observed by scanning electron microscopy.The surface products of the anode alloy were analyzed by energy spectrometer.The open circuit potential,dynamic potential polarization and AC impedance were measured by CHI660E and Autolab PGSTAT204 electrochemical workstation,and discharged by Land battery.The performance test system tested its discharge performance in 4M NaOH solution.The effects of alloying elements Sn,Ga and Mg on the corrosion rate and electrochemical performance of anode alloys were investigated,has been concluded that the Sn and Ga elements were mainly distributed in the form of precipitated phase on the surface of the aluminum anode substrate to act as an active point,which reduced the oxide film resistance of the anode alloy.Because of its high hydrogen evolution overpotential,The Sn and Ga elements can effectively reduce the hydrogen evolution and corrosion of the aluminum alloy anode material.And the alloy anode was transformed from pitting to uniform corrosion;Sn and Ga elements can significantly improve the activation ability of the alloy anode,but in the alloy anode without Mg participation,the anode material can improve its activation ability while its self-corrosion rate also increases together;Mg element can reduce the segregation of Sn and Ga elements in the composition range of 0.5wt%¹.0wt%,so that the distribution of elements on the surface of the substrate was more uniform,the hydrogen evolution rate of the anode alloy decreases.when the composition segregation of Sn and Ga increases to 1.5wt%².0wt%,the self-corrosion rate of the anode alloy increases,and the hydrogen evolution rate of the anode alloy increases.When the Mg content was 0.5wt%,the corrosion current density of the anode material was 5.44±0.7.mA·cm^-2,discharge specific energy was 2549.9 mAh g^-1,which was the best among other Mg content alloy anodes.The electrochemical performance of the anode alloy is optimal;In summary,the composition of the anode alloy with the best electrochemical performance is Al-0.08Sn-0.08Ga-0.5Mg.Under the above research results,the effects of solution treatment and annealing treatment on the corrosion and electrochemical properties of Al-0.08Sn-0.08Ga-0.5Mg anode alloy were investigated by heat treatment.It was concluded that the anode hydrogen alloy has the lowest hydrogen evolution rate when the solution temperature was 450°C+10h.Then,with the increase of solid solution temperature,the hydrogen evolution rate does not changed much,but when the solution temperature was 600°C+10h,the anode alloy burns seriously,and the hydrogen evolution rate of the anode alloy increases.When the solution temperature was 500°C+10h,the anode alloy The corrosion current density was 5.113±0.16mA·cm^-2,the polarization resistance was 3.27Ω·cm²,the discharge specific energy was 3169.7 mWh g^-1,and the discharge efficiency was39.1±0.4%,which is the highest among other solid solution temperature anode alloys.It shows that the best solution temperature of the anode alloy was 500°C+10h.After the annealing treatment,the hydrogen evolution rate of the anode alloy as a whole is increased.The corrosion current density was higher than that of the unannealed anode alloy(5.13±0.6 mA·cm^-2),indicating that the electrochemical activity of the anode alloy was increased,but the corrosion resistance was reduced;the anode was annealed at 350°C+14h.The discharge specific energy of the alloy was 3267.7 mWh g^-1,and the discharge efficiency reaches 39.9±0.4%.The discharge efficiency was highest in all anode alloys.It was higher than the discharge efficiency of most anode alloys on the market（about 35%）.In summary,we have found that the optimum Mg content of Al-0.08Sn-0.08Ga-xMg anode alloy was 0.5wt%,the optimum solution treatment temperature was 500°C+10h,and the optimum annealing temperature was 350°C+14h.