Effect Of Surface Modification On The Electrochemical Properties Of Li₄Ti₅O₁₂ As Anode Material For Lithium Ion Batteries

In the world energy crisis is increasingly prominent today,looking for new alternative energy and high performance energy storage equipment has become a hot research around the world.Lithium titanate(Li₄Ti₅O₁₂,LTO)is a promising battery material featured by its“zero strain”.Lithium titanate as lithium ion battery material has a considerable theoretical specific capacity(175 mAh·g^-1).High and stable electrode voltage to further ensure the lithium titanate battery security and stability.However,lithium titanate battery conductivity and lithium ion diffusion coefficient are relatively low,it is difficult to meet the high rate of charge and discharge,limiting the material in the power battery applications.In this paper,the surface modification of lithium titanate particles in the introduction of carbon layers,other metal oxides such as high conductivity phase,to enhance the diffusion rate of lithium ions and conductivity,improve the electrochemical performance of lithium titanate.Carbon materials are conventional means for surface modification.High conductivity of carbon itself can increase the conductivity of the material;at the same time carbon material has a good pore structure,network structure conducive to lithium-ion transmission to the shape appearance,can enhance the electrochemical properties of materials.In this paper,the titanium dioxide was dispersed in the organic emulsion and the catalyst was used to protect the polypyrrole layer on the surface of titanium dioxide.The precursor was mixed with the lithium source,but the core-shell structure was prepared by high temperature sintering under nitrogen atmosphere.The electrochemical properties of the material were obtained comprehensive upgrade.the discharge specific capacity of 125mAh·g^-1 at 10C and maintain capacity of 95%after 60 cycles at 0.5C,and the diffusion rate of lithium ion reached 2.856×10^-1212 cm² S^-1。When other doping elements are introduced into the LTO matrix,not only the effect on the lattice of lithium titanate,but also some elements on the surface properties of LTO will be affected.Strontium oxide is a small bond material,when combined with other crystals spontaneously in the matrix will take surface enrichment.The surface of the strontium element is prepared to enrich the modified lithium titanate electrode material.Strontium rarely enters the lattice of lithium titanate and spontaneously forms SrO₂ on the surface of lithium titanate,which improves the electrochemical performance of the material.The discharge specific capacity is 188 mAh·g^-1 at 1C current density and 103 mAh·g^-11 at 10C current density,the lithium ion diffusion coefficient is 2.748×10^-12cm²·S^-1.All the data show the excellent electrochemical performance.In addition to strontium with surface enrichment characteristics,cerium elements also have similar characteristics.The ionic radius of cerium ion is closer to that of titanium ion and has better compatibility with lithium titanate.The cerium element was introduced into the preparation of lithium titanate,and the Ce³⁺-doped CeO₂-modified lithium titanate material was obtained.Ce³⁺in the material enters lattice of lithium titanate,enlarges the interplanar spacing,and forms cubic fluorite structure CeO₂ on the surface of the substrate,the synergetic effect of the two influences the material electrochemical performance.10C current density of the material discharge capacity of 120 mAh·g^-1,lithium ion diffusion coefficient 2.01381×10^-1414 cm² S^-1,the first Coulomb efficiency is more than 98%,the modified effect is obvious.