The Effect Of Organic Additive On The Discharge Performance Of Mg Anode

Mg-air battery has great potential for research and development with the characteristics of high theoretical capacitance,high discharge voltage,low anode density and high biocompatibility.However,low anode efficiency is shown in application due to the poor corrosion resistance.The discharge products are easy to deposit on the anode surface and hinder the continuous discharge.In recent years,the key research direction is to solve the above problems by tailoring the electrolyte composition.At present,the research on the improvement of discharge performance by organic additives is still in the exploration stage.The discharge and corrosion behavior of AM50 magnesium anode and pure magnesium anode in electrolyte containing different additives are systematically studied in this work.The influence of high and low Mg2+complex stability constant on the discharge potential of anode is studied.The relationship between anode utilization efficiency,specific capacity,corrosion rate and chunk effect is analyzed.The ability of strong Mg2+complexing agent to reduce the deposition of discharge products on the anode surface is better than that of weak Mg2+complexing agent.It can significantly reduce the discharge potential of anode when used as electrolyte additive.At the current density is 5 mA·cm-2,the average discharge potential of AM50 anode in electrolyte containing 4,5-dihydroxy-1,3-benzenedisulfonate is about-1.73 V.The average discharge potential of pure Mg anode in electrolyte with addition of 5-sulfosalicylic is about-1.82 V when the current density is 2.5 mA·cm-2.The utilization and specific capacity of Mg anode are determined by the weight loss caused by corrosion and"chunk effect".Weak Mg2+ complexing agent(sodium citrate,sodium salicylate,sodium sulfosalicylic)and 5-sulfosalicylic inhibit the "chunk effect" Thus,the anode utilization and specific capacity are improved though the dissolution rate of the anode is increased.The efficiency of AM50 anode was 72.3%in electrolyte containing 0.1 mol·L-1 sodium salicylate at 10 mA·cm-2 current density.On the contrary,due to the high corrosion rate and obvious"chunk effect",the discharge performance of pure magnesium anode in electrolyte containing hydrogen peroxide is poor.However,when the complexing agent is incapable to inhibit the deposition of discharge products on the anode surface,the soluble Mg2+ complexes are easy to adsorb in the discharge products,which are not conducive to the reduction of discharge potential.Moveover,the corrosion resistance of the anode is not improved by 1%hydrogen peroxide and 0.1 mol·L-1 5-sulfosalicylic+1%hydrogen peroxide.The former may be due to the reaction of magnesium with hydrogen peroxide,while the latter may be related to the content of Fe in the sample and electrolyte ratio.