Aluminum Alloy Anode Materials Organization And Electrochemical Performance Study

In this thesis, the characteristics of aluminum as anode material and the development in various kinds of aluminum batteries were firstly reviewed. The effects of alloy elements and heat-treatment to properties of Al alloy anode were overviewed. The self-corrosion rate of Al alloy anode was studied by methods of H2evolution in aqueous medium, while the electrochemical properties of Al alloy anode including open potential curves, galvanostatic discharging curves, dynamic potential measurement, AC impedance, etc were tested using a LK3200electrochemistry test machine. The metallographic microstructures of Al anode were observed using Polyvar-MET metallographic microscope and the incomplete pole figures and ODFs were measured by the Germany’s Siemens D5000X-radio texture analyzer The micrograph of the surface of Al anode reacted in alkaline mediums with or without additives were examined using Sirion200Field Emission SEM coupled with GENESIS60EDS.In this thesis, the influence of adding alloying elements of Ga, Sn, and Pb, Ca, Ba, and Li in Al-Me binary alloy on corrosion rate and electrochemical properties was studied. Orthogonal method optimized the composition of Al-Sn-Ga-Pb alloy. Different heat treatment processes were studied on the optimization of the Al-Sn-Ga-Pb-X aluminum alloy anode material for the corrosion rate and electrochemical properties. At last, the activity mechanism of Al-Sn-Ga-Pb-X alloy anode material was studied. The conclusions are as below.(1) At50℃and in4.5mol/LNaOH+15g/LNa2SnO3media, research on the Al-Me (Ga, Sn, Pb, Ca, Ba and Li) binary alloy we can know the influence of the hydrogen evolution rate:Ga> Li>of Ba, Ca, Pb> Sn; the influence of stable electrode potential:Ga> Sn> Pb＞＞Ca, Ba> Li. In terms of the aluminum alloy anode material, the electrode potential is the more negative the better, and the hydrogen evolution rate is as small as possible. Then it can be optimized that the element of Sn, Pb is better in Al anode. In addition, because of the significant influence of Ga element for the stable electrode potential, and the hydrogen evolution rate of it is in control. Therefore, the elements of Ga, Sn, and Pb were selected for further orthogonal optimization of multi-aluminum alloy anode material. (2) through the orthogonal experiment, we obtained that in the medium of4.5mol/L NaOH+15g/L Na2Sn03, the results show that the greatest impact on the hydrogen evolution rate of aluminum alloy anode material at50℃is Pb, followed by Sn, Ga; at the same time, the greatest impact on the stable potential at50℃and50mA/cm2is Pb, followed by Sn, Ga. After considering and verifying the stable potential and hydrogen evolution rate of aluminum alloy anode, we can obtain the optimal combination:Al-0.05Sn-0.02Ga-0.1Pb. The H2evolution rate is0.062mL min-1cm-2and the stable potential is-1.61V.(3) The influence of the heat treatment process for material properties is different with different material composition.In reply annealing stage (200℃-2h,5h,10h), along with the increase of grain in fiber, Al-Sn-Ga-Pb-X alloy anode material of the formation of hydrogen rate increases, but when the grain increased and brought up in the organization to matrix for small grain after all, the formation of hydrogen rate reduction. The H2evolution rate is0.065mL min-1cm-2and the stable potential is-1.65V.Recrystallization stage (250℃-2h,5h,10h;300℃-2h,5h), with the larger grain size aluminum alloy anode materials for hydrogen evolution rate has been increased. That the entire dynamic process of heat treatment, aluminum alloy anode materials for hydrogen evolution rate first decreases and then increases, and recrystallization annealing to a certain stage, when the matrix structure by a large number of fine grains, aluminum alloy anode materials for hydrogen evolution rate minimum, to approximately0.03mL min-1cm-2, stable electrode potential slightly shifted positively is about-1.62VGrain growth stage (300℃,10h), with the annealing temperature, time, the aluminum alloy anode materials for hydrogen evolution rate increases,0.096mL min-1cm-2, approximately, stable electrode potential slightly shifted negative is about-1.58V.Therefore, after considering the corrosion of the aluminum anode material and electrochemical properties of obtained optimal annealing temperature of250℃, the optimal annealing time is5h～10h.(4) through the activation mechanism of the Al-Sn-Ga-Pb-X aluminum alloy anode material dissolved, the obtained solid solution in Al crystals of Ga, Sn, Al and alkali reaction at the same time, Ga, Sn, and OH" reaction generate soluble GaO2-ion and SnO32-ion the GaO2-ion and SnO32-ion reduction into the elemental Ga deposition of Sn and back to the aluminum surface, the formation of pitting corrosion pit and destroy the Al passive film structure, lower pole of resistance, to reduce the negative polarization, the increase of Al electro-chemical activity.