Study On The Influence Of Rare Earth Salts On Electrochemical Performance Of The Anode Of Aluminum-air Battery

Al-air battery is a new type of high-energy chemical power supply,which usually uses neutral or alkaline electrolyte.It has the characteristics of high energy density,abundant raw materials,low price and long service life,and has a very broad application prospect.However,the self-corrosion of aluminum alloy and the corrosion of corrosive ions greatly shorten the service life of aluminum anode and seriously limit the development and popularization of aluminum-air battery.Adding corrosion inhibitor to electrolyte solution has the advantages of convenient operation,low cost and high corrosion inhibition rate,which is an effective solution.In this paper,the effects of the corrosion inhibition behavior and electrochemical properties of samarium acetate and ytterbium acetate on 7075 aluminum alloy in 3.5%NaCl solution and single cerium acetate,samarium acetate,yttrium acetate,ytterbium acetate and two-phase mixed salts on 5052 aluminum alloy in 4 M NaOH solution were studied by weight loss test,hydrogen evolution test,electrochemical test,microscopic corrosion morphology analysis and constant current discharge.The main results are as follows:The optimal concentration of Sm（OAc）₃ and Yb（OAc）₃ in 3.5%NaCl solution is200 mg/L.The best corrosion inhibition efficiency is 72.22%and 94.28%respectively,but Yb（OAc）₃ is easy to cause anodic passivation.There is a synergistic effect between the two rare earth salts,which can not only achieve a good corrosion inhibition effect,but also cause no anodic polarization,and can obtain good comprehensive properties.Compared with the blank group,when discharging at a constant current density of 20m A·cm^-2,the anode capacity density with rare earth salts increased by 16.3%,from1754.4 m A·h·g^-1 to 2040.8 m A·h·g^-1.Mixed rare earth salts form a composite film by generating hydroxides/oxides of samarium and ytterbium and alternately depositing them on the aluminum surface,which inhibits the self-corrosion and Cl^-pitting of the alloy,reduces the adsorption of intermediates,releases the discharge active sites and improves the discharge performance of the anode.Each rare earth salt obtained the best corrosion inhibition efficiency at 400 mg/L in 4 M NaOH solution,and the order of corrosion inhibition efficiency was as follows:Y（OAc）₃>Ce（OAc）₃>Yb（OAc）₃>Sm（OAc）₃.The addition of rare earth salts reduced the corrosion fluctuation of 5052 aluminum alloy by 4 orders of magnitude,and improved the uneven dissolution of aluminum alloy.During the process of discharging at any current density,the addition of trace rare earth salts reduces the non-discharge loss of the anode and has no obvious effect on the anode activity.Yttrium acetate group has the optimal discharge performance,which anode capacity can be increased by47.6%,30.2%and 18.5%when discharged at current densities of 5 m A·cm^-2,20m A·cm^-2 and 40 m A·cm^-2,respectively.The precipitation particles of different rare earth salts not only have competitive adsorption,but also have synergistic effect when they are mixed.And the corrosion inhibition efficiency is obviously improved compared with that when they are used alone.The corrosion inhibition effect will be greatly improved when Y（OAc）₃ exists in the three-phase mixed salt.And the best corrosion inhibition effect will be obtained when the proportion of Y（OAc）₃ is 60%.