Construction Of Tin/Antimony Metal And Carbon Nanotube Composite Anode Material And Its Sodium Storage Performance

The limitation of lithium resources and cost issues have become a bottleneck for the future development of lithium-ion batteries.Resource-rich,low-cost sodium ion batteries(SIBs)have attracted more and more attention from researchers and are expected to become the next generation of high-performance large-scale energy storage batteries.It is one of the key tasks for the development of SIBs to seek high-specific capacity and long-life sodium storage anode materials.Alloy-based sodium storage anode materials have high theoretical specific capacity and suitable sodium insertion potential,which have attractive research potentials.At present,they mainly have the problem of extremely poor cycle stability due to the volume effect.Based on this,this thesis uses the functionalized carbon nanotubes as the matrix,and uses the solution immersion method combined with the reduction treatment to construct an alloy/carbon nanotube composites,and study its sodium storage performance and its charge-discharge mechanism.The main findings are as follows:Preparation of metal tin/carbon nanotube composites and research on its sodium storage performance.Using functionalized disordered carbon nanotubes(CNTs)as the carbon skeleton and anhydrous tin tetrachloride as the tin source,Sn/CNTs composites were prepared by solution impregnation and reduction.Among them,Sn/CNTs(N₂H₄)composite material has good cycle stability.At a current density of 1 A g^-1 for 500charge-discharge cycles,the capacity retention rate is 73.9%,and the average attenuation per cycle is only 0.1075 m Ah g^-1(compared with the capacity after 100cycles).The preparation of Sb/HPACNTs composites and its sodium storage performance.After pore-forming and acidizing the aligned carbon nanotubes,a hierarchical hole-oriented carbon nanotube array(HPACNTs)is formed.Using this as a carbon matrix,Sb/HPACNTs composites were prepared through solution immersion,melt diffusion and high-temperature thermal reduction.In the optimized Sb/HPACNTs-7 composites,Sb is mainly distributed in the cavities of the aligned carbon nanotubes,the pores of the tube wall and between the tubes.At a current density of 1 A g^-1,the specific charge capacity after 4500 cycles is 318 m Ah g^-1,and the average capacity decay per cycle is only 0.08 m Ah g^-1.The ex-situ XRD,TEM and SEM results show that during the sodium storage process,a stable SEI film can be formed on the outer surface of the carbon nanotubes.During the charge and discharge process,the powdered active material Sb exists in the carbon nanotubes as particles of about 2 nm cavity.Its ultra-long cycle stability is mainly attributed to the physical confinement of carbon nanotubes,which effectively suppresses the volume effect.This work has laid a solid theoretical foundation for the further research of alloy-based sodium ion battery anode materials,and can also provide ideas and guidance for the research of other new sodium/potassium ion battery electrode materials that have volume effects during charge and discharge.