Effects Of Fe,B And Mn On Properties Of Anode Alloys For Aluminum-air Battery

With the development of science and technology and the progress of society,the environmental problems caused by the uncontrolled use of traditional energy sources have attracted more and more attention.Aluminum-air battery is the most new energy utilization method.With its advantages of large theoretical capacity,high unit energy,abundant raw material reserves,safe and environmentally friendly products,it has become a research hotspot for researchers.In order to obtain a larger current density,aluminum-air batteries generally use a strong alkaline solution as the electrolyte.However,the aluminum anode is easily corroded in the strong alkaline solution.The chemical reaction that occurs during the corrosion process generates heat that causes the temperature of the electrolyte to rise,leading to anode corrosion More serious,releasing more heat,causing the electrolyte temperature to fall into a vicious cycle of further rise.This not only shortens the service life of the battery,but also greatly reduces the utilization efficiency of the battery anode.At the same time,a large amount of hydrogen released may also cause serious safety problems,which need to be studied and solved urgently.In this paper,high-purity aluminum is used as the base alloy.The effect of impurity Fe on the corrosion resistance,electrochemical performance and anode efficiency of alloy samples is explored by adding Fe element.Then using standard aluminum as the base alloy,B and Mn elements were added to study the removal effect of impurity Fe element in the aluminum matrix,and the effects on the corrosion morphology,electrochemical performance and anode efficiency of the anode alloy.During the experiment,the content of each component in the alloy was detected by inductively coupled plasma mass spectrometry(ICP-MS),and the corrosion morphology of the anode alloy sample was observed by an electron scanning microscope(SEM).The H2 evolution corrosion rate was measured using electrochemical workstations to test the open circuit potential,polarization curve,EIS spectra,and galvanostatic discharge curves of the anode alloy,and the weightlessness method was used to measure the anode efficiency of the battery.The experimental results show that with the increase of Fe content in high-purity aluminum,the activation performance and corrosion resistance of the alloy are greatly reduced.When using high-purity aluminum with a Fe content close to 0 as the negative electrode,the overall performance of the obtained alloy is the most good.In 4 mol/L KOH solution,the corrosion morphology of the anode alloy was flat,and the hydrogen evolution corrosion rate was 0.081 mL·cm-2·min-1;the open circuit potential was-1.689 V(vs.HgO/Hg);the corrosion potential was-1,669 V(vs.HgO/Hg);corrosion current density is 15.894 mA·cm-2;galvanostatic discharge curves is performed at a current density of 100 mA·cm-2,and the discharge voltage is-1.687 V(vs.HgO/Hg).By fitting the EIS spectra,it was found that the high-frequency capacitive arc resistance and intermediate-frequency capacitive arc resistance modes of the negative electrode samples became larger,and the corrosion resistance was improved.The anode efficiency of the battery reached 80.67%,which was 3.39 times that of the standard aluminum anode.Adding B element to standard aluminum has obvious effect on removing Fe element from the alloy,which reduces the activation performance of the alloy to a certain extent,and greatly improves the corrosion resistance of the alloy.When the B content is 0.3%,the overall performance of the obtained negative electrode alloy is the best.At this time,the content of Fe element in the negative electrode alloy was reduced to 0.057%,the H2 evolution corrosion rate was 0.130 mL·cm-2·min-1,and the corrosion morphology was uniform;the open circuit potential was-1.348 V(vs.HgO/Hg),and corrosion current density is 20.097 mA·cm-2;the constant current discharge is performed under the condition of a current density of 100 mA·cm-2,and the discharge voltage is-1.383 V(vs.HgO/Hg).The electrochemical diffusion resistance Rc obtained by fitting the EIS spectra of the alloy increases,and the corrosion resistance of the alloy is enhanced.The anode efficiency of the battery reaches 78.71%,which is 3.31 times that of standard aluminum,which is equivalent to 97.57%of the high-purity aluminum anode efficiency.Adding Mn element to standard aluminum improves the electrochemical activity of the alloy and increases the corrosion resistance first and then decreases.When the Mn content is 0.3%,the comprehensive performance of the obtained alloy increases the most.The corrosion rate of H2 evolution was 0.147 mL·cm-2·min-1,and the corrosion morphology was improved;the open circuit potential was negatively shifted to-1.490V(vs.HgO/Hg);the corrosion potential was-1.504V(vs.HgO/Hg),The alloy’s electrical activation performance is enhanced;corrosion current density is 8.1 mA·cm-2;constant current discharge is performed at a current density of 100 mA·cm-2,and the potential is-1.507 V(vs.HgO/Hg).The electrochemical diffusion resistance Rc obtained by fitting the EIS spectrum of the alloy increases,and the corrosion resistance of the anode alloy is improved.The anode efficiency of the battery is 29.13%,which is 24.6%improvement over standard aluminum.