Surface Modification And Sodium Storage Of Three Dimensional Antimony Electrode

Metallic antimony has shown tremendous application prospect in sodium-ion batteries owing to its high theoretical specific capacity(660 m Ah g^-1)and moderate work potential(0.6V vs.Na/Na⁺).Nevertheless,the serious volume expansion and shrinkage during the sodiation and desodiation processes induce instability of electrode/electrolyte interface,exfoliation of active materials,and finally result in rapid capacity fading.To solve these issues,this dissertation constructed antimony-based electrodes by three dimensional structural design and surface modification,which could effectively suppress the volume variations upon sodiation/desodiation processes,and realize high specific capacity,superior cycle stability and rate performance.The main research is given in the following.(1)The three dimensional(3D)porous Sb is prepared by electrodepositing using 3D porous Cu as the substrate.Then,an Indium layer is electrochemical coated on the surface of3D porous Sb,coupled with surface chemical passivation to construct 3D porous Sb@In₂O₃electrodes.The porous architecture could alleviate the volume and stress changes upon sodiation/desodiation processes,which could ensure the structure stability of electrodes.Moreover,the In₂O₃coating could stabilize the electrode/electrolyte interface,which could also keep the structure stability.As the anode of sodium-ion battery,the 3D porous Sb@In₂O₃shows a high first Coulombic efficiency of 85.3%,a reversible capacity of 456.5 m Ah g^-1remained after 300 cycles at 300 m A g^-1,a high reversible capacity of 348.9 m Ah g^-1even at a high current density of 20 A g^-1.(2)The 3D Sb nanowires are fabricated by electrodepositing Sb film on the 3D porous Cu nanowires prepared by anodizing process,and its morphology is controlled by adjusting the concentration of Sb³⁺.The Sb film deposited in low Sb³⁺concentration(0.04M)shows smaller crystal grains and better coating performance.It delivers a reversible capacity of424.9 m Ah g^-1 after 200 cycles at 300 m A g^-1,which is significantly higher than that of Sb electrode prepared in high Sb³⁺concentration(341.2 m Ah g^-1)under the same conditions.Moreover,the 3D Sb nanowires@In₂O₃ electrodes are obtained by electrodepositing an Inium layer on the surface of 3D Sb nanowires,coupled with surface chemical passivation.The electrochemical performance results show that it remains 525.1 m Ah g^-1 after 160 cycles at1000 m A g^-1,a reversible capacity of 578.9 m Ah g^-1even at a high current density of 6000m A g^-1.The improved performance can be attributed to its unique morphology,in which the sufficient spaces between the nanowires are beneficial to buffer the volume changes during the sodiation/desodiation processes,the presence of In₂O₃ coating layer simultaneously facilitates stabilizing the electrode/electrolyte interface.(3)The polypyrrole coating layer is coated on the surface of Sb nanowires by in-situ chemical polymerization.This electrode delivers a reversible capacity of 460.5 m Ah g^-1 at500 m A g^-1 over 240 cycles,a reversible capacity of 461 m Ah g^-1 can be maintained even at a high current density of 6000 m A g^-1.The excellent electrochemical performance is mainly attributed to its unique structure,in which the 3D nanowires and PPy coating layer can synergistically relieve the volume variation effect during the sodiation/desodiation processes,and the PPy coating layer can also prevent the direct contact between the electrolyte and Sb.