Modification And Electrochemical Performance Of Silicon Anode Materials

Silicon based anode material has the highest mass specific capacity(4200mAhg-1)at present,and has a advantage of wide range of sources,easy to prepare,so it is an ideal anode material for the next generation of battery.But suffering from the huge volume expansion during lithiation and delithiation,which will cause the electrode materials to be pulverized and shedding,this is the most enormous challenge for silicon anode materials.In view of the problem,this paper,nano-silicon is used as the raw materials,which is wrapped in the three-dimensional network of VGCF;Silicon/polypyrrole composites were prepared by surface modification,which made hydroxyl and amino groups on the surface of nano silicon and covered with polypyrrole;the silicon/graphene composite material is prepared through the self-assembly characteristics of graphene oxide,the modified nano-silicon is loaded in the three-dimensional graphene network.The structure and electrochemical performance of the three materials were tested by SEM,TEM,TGA,XRD,FT-IR and electrochemical tests.By means of ball milling,silicon and different rations of Super-p/VGCF,it is found that when the VGCF completely replace the Super-P,the electrochemical performance is the best.After 50 cycles,the reversible specific capacity is as high as 1206mAhg-1.The effect of functional group on the effect of coated polypyrrole was investigated by coating polypyrrole coating on the outer layer of nano silicon.It was found that when the surface had more hydroxyl groups,the carbon layer of polypyrrole was thicker.After 50 cycles,the reversible specific capacity was up to 946.2mAhg-1.On this basis,we further covered the thicker polypyrrole carbon layer on the hydroxyl silicon surface,and found that the electrochemical performance also improved.After the 50 cycle,the reversible specific capacity was up to 1238.2mAhg-1.On the basis of modification,we have encapsulated nano-silicon in graphene network structure by hydrothermal reduction,and prepared Si/Graphene composites.The composite exhibits the best cycling performance.After 50 cycles,the reversible specific capacity is as high as 1896mAhg-1.