Research On The Structure Design And Li~+/Na~+/K~+ Storage Properties Of Sb-based Composites

Recently,lithium-ion batteries（LIBs）has been widely used in many fields.However,the maldistribution of lithium resources and high cost have been increasingly emerging from day to day.As the alkali metal elements sodium and potassium,which are the same main group as lithium,possess the advantages of abundant source and low cost.If high-performance sodium/potassium ion batteries（SIBs/PIBs）can be constructed,they will have great prospects in the future energy storage battery application market.Graphite shows poor Na⁺/K⁺storage properties,so it is important to find suitable anode materials for SIBs/PIBs.Sb-based materials have become one of the most potential anode materials due to their advantages of high specific capacity、wide sources、high safety and suitable voltage platform,but their poor mechanical and dynamic properties hinder their practical application.Herein,this paper carries out research from improving synthesis methods、optimizing structure and exploring energy storage mechanism for material.The specific research content and results are as follows:（1）The Sb nanoparticles were successfully encapsulated in a carbon matrix containing N、S and F co-doping by solvothermal and high temperature solid-state reduction methods to obtain the composite（Sb@NSF-C）,and the Sb@NSF-C exhibited excellent electrochemical storage behavior of Li⁺/Na⁺/K⁺.For example,it can provide a specific capacity of 375 m Ah g^-1after 400 cycles at a high current density of 1 A g^-1for LIBs.A capacity of 180.7 m Ah g^-1can be remained at 1 A g^-1after 200 cycles in SIBs.In addition,a capacity of 290 m Ah g^-1can be obtained at 1 A g^-1after 200 cycles in PIBs.The change of microstructure of Sb@NSF-C composite before and after charge and discharge process was studied by in-situ XRD method,and the mechanism of Li⁺/Na⁺/K⁺storage for the composite was explored.Simultaneously,the intrinsic relationship between the unique microstructure design and electrochemical performance was illustrated.In other words,the3D porous structure can effectively alleviate the structural changes of Sb phase.More importantly,N、S and F co-doping can not only offer more carbon defects,improve more Li⁺/Na⁺/K⁺active adsorption sites,but also improve the electrical conductivity of the material.Thus,the performance of active Sb storage Li⁺/Na⁺/K⁺can be improved effectively.（2）The confined growth of Sn Sb nanoparticles was obtained by using polypyrrole（PPy）and outer carbon as internal and external support skeleton,and Sn Sb alloy was successfully encapsulated in N doping carbon matrix to prepare the composite（NC@Sn Sb@NC）.Luckly,the NC@Sn Sb@NC can show excellent Li⁺/Na⁺/K⁺storage properties.It can provide a capacity of 402.7 m Ah g^-1at 10 A g^-1.After 1500 cycles,the capacity can still be obtained at 467 m Ah g^-1at 1 A g^-1in LIBs.The capacity of 386 m Ah g^-1can be retained at 1 A g^-1after 120 cycles in SIBs.Similarly,a capacity of 236 m Ah g^-1can still be obtained at 1 A g^-1after 500 cycles in PIBs.Combined with density functional theory（DFT）analysis,the outstanding electrochemical performance is attributed to the presence of mechanical stable carbon matrix,which can not only achieve high conductivity,but also inhibit active Sn Sb particle agglomeration、enhance the high efficiency ion storage behavior.（3）A ternary Sb₂O₃-Fe-C composites（SFC）with high capacity and stability were constructed via a simple mechanical alloying method.The experimental results suggested that the SFC anode can possess excellent electrochemical performance along with the initial Coulomb efficiency（ICE）of 83.8%at 0.5 A g^-1for LIBs.Even at 10 A g^-1,the capacity can be maintained at 680.3 m Ah g^-1.Similarly,the excellent cyclic stability was also revealed in SIBs/PIBs.Through a variety of characterization methods and DFT analysis,the carbon materials can alleviate the volume expansion and improve the overall electrical conductivity with Fe.More importantly,the active Fe particles are also beneficial to catalyze the Li-O（Na-O/K-O）bond and Sb-O bond fracture、reduce the activation energy and improve the ICE of the battery to obtain remarkable performance.