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Design And Preparation Of 3D Network Structure TiO2 Nanowire Composite Sn And Its Lithium Storage Performanc

Posted on:2024-03-19Degree:MasterType:Thesis
Country:ChinaCandidate:B N DengFull Text:PDF
GTID:2531307109998279Subject:Materials and Chemical Engineering (Professional Degree)
Abstract/Summary:PDF Full Text Request
With the development of society,people urgently need lithium batteries with fast charging,long life and high energy density.However,at present,the ion migration rate of commercial graphite materials is slow,so the rate performance of graphite materials as negative electrode batteries is relatively low.In addition,during the use of the battery,the insertion and removal process of lithium ions in the graphite material will cause the deformation of the graphite material(about 10%),which will affect the cycle life of the battery.So,people turned their attention to TiO2 electrode materials.TiO2 has attracted much attention as an anode material for lithium-ion batteries with high rate performance and long cycle life.However,due to the low differential conductivity and capacity of its metal oxides,TiO2 anode materials have not been commercialized until now.Graphite anode materials not only have slow charging,short life,but also low energy density.Therefore,people are also concerned about lithium metal anodes,which have great potential.Lithium metal anode is deeply attracted by people’s continuous exploration because of its high energy density and lowest potential.However,because lithium metal anode batteries will produce uncontrolled lithium dendrites and dead lithium,which is easy to cause serious battery accidents,it has not been widely popularized.Once the problems of TiO2 anode materials and lithium metal anodes are improved,the two are undoubtedly the best candidates as the next generation of energy storage materials.In this paper,3D reticular TiO2 nanowires(r-Sn/TiO2)loaded with Sn metal were prepared by hydrothermal and electroless plating,and its advantages in lithium-ion battery anode materials and lithium metal anode scaffolds were discussed,such as high specific surface area,shortening the diffusion path of lithium ions,reducing the nucleation barrier of lithium deposition and inhibiting the growth of lithium dendrites.Details of the study are as follows:(1)In this paper,the r-Sn/TiO2 composite electrode material is designed for the low conductivity and low capacity of TiO2 anode materials.By making the active material in closer contact with the collector,shortening the lithium-ion diffusion distance and enhancing the electronic conductivity characteristics,while the loaded Sn metal particles increase the capacity,and the conductivity and pseudocapacitance are improved by using the nanoscale network structure and the synergistic contribution of Sn and TiO2 in the structure.The electrode material has a higher discharge capacity or rate discharge capacity.From the electrochemical results,the pseudocapacitance characteristics brought by the high specific surface area of r-Sn/TiO2 make the material exhibit excellent reversible capacity,and at a current density of 200 m A g-1,it can still maintain a coulomb efficiency of about 99%after the 400th cycle.Under the dual active material strategy of Sn and TiO2,r-Sn/TiO2 exhibits lower impedance and higher capacity.At the same time,the high specific surface area of the self-supporting three-dimensional nanostructure brings a highly active interface to the electrode,promotes the rapid transport of lithium-ions,and makes the electrode show excellent long-cycle ability at high current density.While accelerating the chemical reaction,it also intensifies the rate of side reactions,so that a large amount of SEI film is generated at the electrode,which consumes a large amount of lithium ions and reduces the energy density of the battery.To this end,the composite material is also pre-lithiated(a short-circuit-like self-discharge mechanism)to generate a dense SEI film before the electrode cycle.Through the study of time variables,the first circle coulombic efficiency was close to 100%after 30 min of prelithiation,and scanning electron microscopy and transmission electron microscopy studies showed that the nanostructure of r-Sn/TiO2 was maintained after prelithiation.At the same time,the lithium sheets used in the experimental process are nearly 100%reused,and the whole process is an economical and convenient process.(2)With the excellent interface layer and self-supporting three-dimensional structure of r-Sn/TiO2 composites,the r-Sn/TiO2 composites should be applied to lithium metal anode batteries,and from the results,they show excellent battery performance.The composite material has a low Sn loading(Sn≈5%)on the lithium metal anode holder,which is an economical and convenient preparation method for preparing lithium metal anode.The prepared three-dimensional lithium metal anode scaffold has a low nucleation barrier and a long stable cycle,in addition,it can accommodate a large amount of lithium metal in the three-dimensional frame while making lithium deposition uniform and dendrite-free growth.The Sn loading on the TiO2 skeleton lowers the nucleation potential barrier of Li,making Li deposition denser and smoother on the surface.At a current density of 0.5 m A cm-2,the nucleation overpotential of the r-Sn/TiO2 electrode is as low as 19 m V.A stable cycle of over 2000 hours was achieved at a current density of 0.3 m A cm-2 with a coulomb efficiency of~98%.The r-Sn/TiO2 electrode can be stably deposited for more than 50 cycles at a high deposition capacity of 5 m Ah cm-2.
Keywords/Search Tags:lithium-ion battery, lithium metal anode, TiO2, Sn, 3D structural design
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