Effect Of Pickling On Surface Morphology And Electrochemical Performance Of Anode In Magnesium Secondary Battery

Compared to lithium-ion batteries,Magnesium secondary batteries have such more advantages such as Low cost,high safety,environmentally friendly,which is expected to play a role in large-scale energy storage.However,magnesium is easy to form oxide film,which seriously restrict the electrochemical performance of magnesium batteries.It is an urgent problem to improve the electrochemical performance of magnesium battery by removing oxide film on surface quickly,conveniently and at low cost.In this study,pure magnesium and AZ31 were selected as research objects to study the effects of six acids（sulfuric acid,nitric acid,phosphoric acid,citric acid,oxalic acid and acetic acid）on the surface morphology,element distribution,roughness and corrosion properties of materials,and the application of pickling process in the field of magnesium secondary battery anode surface treatment.The main research contents and conclusions are as follows:Under the same conditions,the surface roughness value of AZ31 after pickling is higher than that of pure magnesium,and the effect of pickling on the surface corrosion of AZ31 is greater.The surface roughness of pure magnesium after pickling with nitric acid and oxalic acid is lower,The surface roughness of pure magnesium after pickling with nitric acid and oxalic acid is lower,the surface element distribution is uniform and the corrosion resistance is improved.The surface roughness and corrosion current density of pure magnesium after pickling with sulfuric acid are larger.For AZ31,The surface roughness after nitric acid pickling is the lowest.Sulfuric acid,phosphoric acid,citric acid pickling make the surface corrosion resistance of AZ31 worse,other acids have little influence on the surface corrosion of AZ31.At 0.2 m A cm^-2,the overpotential of pure magnesium can reach 0.05 V and that of AZ31 can reach 0.1 V.With the improvement of polishing accuracy,the battery needs less time to reach the stable overpotential.The overpotential of magnesium symmetric battery after oxalic acid pickling is 0.04 V,and that of AZ31 symmetric battery after sulfuric acid pickling is 0.08 V,which all lower than the stable overpotential of the battery after grinding with 1200 mesh.Nitric acid pickling of pure magnesium and AZ31 symmetrical cells was the fastest to achieve stability.Pure magnesium as anode,nitric acid pickling process can be used,oxalic acid pickling process needs to be further improvement,sulfuric acid pickling process is not suitable.The performance of galvanostatic charge-discharge,potential difference of cyclic voltammetry curve and efficiency of deposition/dissolution after pickling with different concentration of nitric acid can reach the treatment effect of 1200 mesh grinding.With the increase of nitric acid concentration,the surface roughness value of pure magnesium decreases,the AC impedance of symmetrical battery decreases,the surface morphology of charge and discharge is smoother,the loose oxidation products are less,and the capacity of the whole battery is almost the same as that of the battery after grinding with 1200 mesh.Under the same condition,after oxalic acid pickling,the overpotential of symmetric cells decreases to 0.04 V,but the efficiency of deposition/dissolution is not stable.After acid pickling with different concentration of sulfuric acid,the charge-discharge curves of symmetrical batteries show more chaotic,which may be caused by the complex surface topography after acid pickling.AZ31 as anode,nitric acid pickling can be applied,oxalic acid and sulfuric acid pickling is not suitable.The surface of AZ31 after pickling with different concentration of nitric acid is smoother,and the oxide of surface is less after charge and discharge.The performance of galvanostatic charge-discharge,potential difference of cyclic voltammetry curve and efficiency of deposition/dissolution after pickling with different concentration of nitric acid can reach the treatment effect of 1200 mesh grinding,and the long cycle performance is more excellent.The first cycle discharge specific capacity of AZ31|Cu S full battery were 198 m Ah/g,184 m Ah/g,344 m Ah/g and 329 m Ah/g,which AZ31 anode is processed by sulfuric acid,oxalic acid,nitric acid pickling and hand-polished 1200 mesh.Nitric acid pickling can effectively maintain its capacity,sulfuric acid and oxalic acid pickling process can not meet its requirements.Compared with the cost,time,material waste,resource consumption and other problems caused by grinding,pickling can effectively replace and achieve good results.For pure magnesium and AZ31 as anode of magnesium secondary battery,nitric acid pickling process is better.