Study On Modification And Electrochemical Properties Of Mg₂Ni Hydrogen Storage Alloy By Graphene And FeB

Mg₂Ni has a strong hydrogen adsorption capacity and a large theoretical hydrogen storage content.Using it as a hydrogen storage material carrier by an electrochemical hydrogen storage method is expected to realize the reversible hydrogen storage of hydrogen energy.However,Mg₂Ni alloys have poor hydrogen storage kinetics and cycle stability,and are used for battery materials in harsh discharge conditions,which limit their practical applications.There searches have found that the hydrogen absorption or desorption rate and electrochemical performance of magnesium-based hydrogen storage materials can be improved by adding catalysts.Therefore,on the basis of systematically reviewing the research status of hydrogen storage properties and electrochemical properties of Mg₂Ni alloys,in this paper,a series of Mg₂Ni composite hydrogen storage materials were prepared by doping G（graphene）and Fe B into Mg₂Ni alloy by adding catalyst by wet ball milling.In the end,the three materials were jointly ball-milled to prepare double-doped Mg₂Ni composites,and it was found that the double doping of G and Fe B effectively improved the electrochemical properties of Mg₂Ni hydrogen storage alloys.（1）Doping different contents of G into Mg₂Ni alloy,it was found that the maximum discharge capacity of the composite electrode was increased,and the capacity retention rate was also improved.Among them,the maximum discharge capacity of Mg₂Ni+10wt.%G composite electrode is the largest among all composite materials,which is 176.60m Ah/g,which is 47.30%higher than that of Mg₂Ni hydrogen storage alloy.Compared with Mg₂Ni hydrogen storage alloy,the self-discharge capacity loss of G-added composites is lower,and the high-rate discharge performance is improved.For the composite material with the best hydrogen storage performance,the ball milling time is about 10 hours,and the G doping amount is in the range of 5wt.%～10wt.%.（2）Fe B has a high discharge capacity（1359.35m Ah/g）,and it is doped with Mg₂Ni alloy.The maximum discharge capacity of the alloy continues to increase as the proportion of Fe B in the material increases,and the capacity retention rate increases with the amount of Fe B doping.Decreases begin to appear above 50 wt.%.The HRD value of Mg₂Ni+30%Fe B composite alloy at high current discharge density is larger than that of the two alloys alone.After being charged with the same amount of electricity and left open for 5×24 hours,the CRT value of Mg₂Ni+30%Fe B is 99.90%,with almost no capacity loss.（3）Doping G and Fe B in Mg₂Ni alloy at the same time shows that the maximum discharge capacity（435.20m Ah/g）of Mg₂Ni+30wt.%Fe B alloy electrode is improved by doping G,but the loss of self-discharge capacity increases.From the surface morphology of the alloy,it is known that the alloy material becomes looser after doping with G,which causes the electrolyte to corrode the Fe B and Mg₂Ni alloys.