Synthesis And Application Of Hierarchical Antimony/Carbon Micro-/Nanohybrid Lithium/Sodium-ion Battery Anodes

With increasing demand to rechargeable batteries in global energy market,it is crucial to develop alternative anode materials with higher energy/power densities and longer cycling lives.Antimony?Sb?has been regarded as a promising alternative lithium/sodium-ion battery anode due to its high specific capacity(660 mAh g^-1)and appropriate voltage profile?0.8 V-0.9 V vs.Li/Li⁺,0.5 V-0.8 V vs.Na/Na⁺?.However,drastic volume change causes a poor cyclic stability,which significantly impedes its practical applications.Various strategies have been proposed to address this issue including decreasing particle size,creating hierarhical structures and compositing with buffer materials.In this thesis,synthesis of antimony nanoparticles is combined with composition with carbon matrix to improve the electrocehmcial performance of the antimony based lithium/sodium-ion battery anodes.To achieve this aim,a facile scalable synthesis of hierarchical Sb/C micro-/nanohybrid has been developed in this work,which possesses the advantages of both micrometer and nanometer scale structures.The main results of this thesis are summarized as following.Firstly,scalable synthesis of hierarchical Sb/C micro-/nanohybrid anode material has been developed.Difunctional methacrylate monomers are used as both solvent and carbon source.Liquid precursor of antimony?III?n-butoxide is dissolved in the resin monomer solution,and further incorporated into the cross-linking polymer network via photo polymerization.Through calcination in argon/hydrogen atmosphere,antimony nanoparticles are in situ formed by carbothermal reduction,and homogeneously embedded in the in situ formed micrometer sized carbon matrix.The cyclic and rate performance of the Sb/C micro-/nanohybrid lithium-ion battery anode have been effectively improved compared to the pure carbon anode.A reversible capacity of 362 mAh g^-1 is achieved with a reasonable mass loading density after 300 cycles at66 mA g^-1,corresponding to capacity retention of 79%.With reduced mass loading density,the reversible capacity reaches 793 mAh g^-1 after 100 cycles.Moreover,the electrochemical performance of the Sb/C micro-/nanohybrid as sodium-ion battery anode is also investigated in this thesis.Secondly,the control over strcutrue and performance of the hierarchical Sb/C micro-/nanohybrid has been investigated further,where series of different calcination temperatures and times have been applied in this thesis.It has been found that with either an excessive calcination time or a temperauture below or above the melting point of the antimony leads to deteriorated electrochemical performance.The procotol of calcination at 600?C for 10 hours generates the best overall electrochemical performance.Thirdly,carbon dioxide activation is applied on the as-synthesized antimony/carbon micro-/nanohybrid materials to further improve the rate performance.The carbon dioxide activation process introduces mesopores into the Sb/C micro-/nanohybrid and enhances its specific surface area.As a result,the rate performance is signigicantly improved.Besides,the Sb/C hybrid materials treated with the carbon dioxide activation process is also utilized as sodium-ion battery anode,which shows a good electrochemical performance as well.