Research On The Reaction Mechanism And Performance Of Al-Mg-Sn Alloy Anode For High Power Aluminum Air Battery

As a kind of green energy source,the aluminum-air battery has the advantages of abundant storage capacity,low cost and high safety,which is an ideal emergency backup power source.However,the existence of interfacial passivation and self-corrosion of aluminum anodes in the electrolyte leads to the actual discharge power and specific capacity of aluminum-air batteries being much lower than theoretical values.Anode micro-alloying was one of the effective ways to improve the electrochemical activity of the aluminum anode interface.Therefore,in this research,Al-Mg and Al-Mg-Sn anode alloys were prepared by melting method.Microscopic characterization techniques and electrochemical analysis were used to study the anode/electrolyte interfacial reaction.A simple model of the anode/electrolyte interface was proposed.Based on the interface model,Mg and Sn elements were added to pure aluminum,the electrochemical and the battery performance tests were performed.The electrodes with the best performance were selected and assembled into battery monoblocks to regulate the operating conditions for high power optimization tests.A simplified model of the structure of the pure aluminum anode/solution interface was established by Electrochemical Impedance Spectroscopy and scanning electron microscopy techniques.The mechanism of the influence of parameters such as electrode potential,electrolyte concentration,temperature and C₆H₁₂O₆additive concentration on the interfacial reaction was investigated.The interfacial structure of the anode in KOH solution consists of a passivation film and a porous corrosion product layer.The change of the double electric layer at the interface between the cathode and the electrolyte caused the change of the high frequency capacitive resistance arc in the Electrochemical Impedance Spectroscopy impedance spectrum.The mass transfer process at the electrode interface during the electrochemical reaction caused a change in the low-frequency capacitive resistance arc.This paper investigated the effect of Mg and Sn content on the hydrogen precipitation corrosion and surface passivation of aluminum anode,and the results showed that with the increase of Mg content,the hydrogen precipitation corrosion rate in Al-xMg alloy was suppressed,the corrosion resistance was improved,the open circuit voltage and self-corrosion voltage were negatively shifted,and the discharge energy density and power density were increased.The addition of low melting point Sn elements can further improve its electrochemical properties.As the Sn content in Al-2Mg-xSn alloy increases,the solid solution Mg content decreases and the Mg₂Sn precipitation phase content increases.The hydrogen precipitation corrosion rate showed a trend of first decreasing and then increasing,and the open circuit voltage and self-corrosion voltage shifted negatively and then positively.The addition of 0.15 wt.%Sn element further improved the power density and energy density,and the negative discharge utilization rate increased.In response to the problems of low power density and low energy density of conventional alkaline aluminum-air batteries,an aluminum-air battery structure scheme with micro anode-cathode distance and electrolyte circulation flow was adopted on the basis of Al-2Mg-0.15Sn anode.The study showed that lowering the anode-cathode distance,increasing the electrolyte temperature and proper electrolyte circulation flow rate can improve the power density and discharge voltage of aluminum air battery.The ideal operating conditions of aluminum air battery were pole distance of 3 mm,air atmosphere,circulating electrolyte flow rate of 20m L·min^-1and electrolyte temperature of 65℃.At this time,the discharge voltage has been increased by 24-52%at 30-120 m A·cm^-2,and the ultimate current density of the battery was close to 550 m A·cm^-2and the ultimate power density was about432.3 m W·cm^-2.