Research On Modification And Electrochemical Performance Of Spinel Li₄Ti₅O₁₂

Li₄Ti₅O₁₂（LTO）is considered to be a promising titanium-based anode material for lithium ion batteries due to its outstanding safety performance and excellent cycle stability.However,LTO itself has poor electronic conductivity and low lithium ion diffusion coefficient.These two disadvantages severely inhibit its electrochemical activity and restrict its application and promotion in high-power lithium-ion batteries.Considering the good conductivity of rGO and high surface activity,high specific capacity of TiO₂,we modified LTO with rGO and TiO₂ to facilitate the insertion/extraction process of lithium ions and electrons in LTO,which significantly enhanced its electrochemical performance.In addition,the LTO structure with small particle size and regular morphology can provide sufficient active sites for electrochemical reactions and accelerate the transport of lithium ions and electrons.Therefore,in order to further enhance the electrochemical performance of LTO,the paper mainly studies the modification of LTO by the construction of nanostructures and the composite of rGO,TiO₂.First,we successfully synthesized Li₄Ti₅O₁₂ quantum dots/rGO（LTO QDs/rGO）composite by solvothermal method.LTO was uniformly embedded in a two-dimensional rGO nanosheet structure in the form of quantum dots（QDs）for the first time,which utilized the ultra-small particle size of LTO QDs and the good electronic conductivity of rGO,providing more active sites on the LTO surface.The point can facilitate the embedding of lithium,greatly promoting the migration of Li⁺and electrons to enhance the lithium storage capacity of the material.In the voltage range of 1.0-2.5 V（vs.Li⁺/Li）,LTO QDs/rGO has a reversible capacity of 188.9 mAh g^-1 at1 C,and even at a high rate of 30 C,it still has a reversible capacity of about 156.1mAh g^-1.LTO QDs/rGO composite will have great potential as a new titanium-based material to meet the needs of high-power energy storage.In addition,we have successfully synthesized a porous titanium dioxide-modified lithium titanate composite（LTO/TO-R）by a simple solvothermal and heat treatment method in a diethylene glycol-water composite solvent system.When the LTO/TO-R was used as a negative electrode for lithium-ion battery,the material exhibited excellent electrochemical performance because the theoretical specific capacity of TiO₂ was high and the phase interface provided more active sites.In the voltage range of 1.0-2.5 V（vs.Li⁺/Li）,the LTO/TO-R composite had a reversible capacity of 177.5 mAh g^-1 at 1 C,and even at a high rate of 30 C,it still had a reversible capacity of about 140.8 mAh g^-1.We believe that the LTO/TO-R composite will have broad application prospects in the new generation of lithium-ion batteries.Finally,on the basis of the previous period,we successfully synthesized LTO/TiO₂-Rutile Nanosheets/rGO composite（LTO/TO-R NSs/rGO）by solvothermal and heat treatment methods using CTAB as the structure-directing agent.In the voltage range of 1.0-2.5 V（vs.Li⁺/Li）,LTO/TO-R NSs/rGO had a reversible capacity of 186.5 mAh g^-1 at 1 C,and even at a high rate of 30 C,it still had a reversible capacity of about 146.8 mAh g^-1.This section uses a multi-phase recombination strategy.The rich phase interface and grain boundary can store additional Li⁺,which will significantly improve the high rate performance of LTO.LTO/TO-R NSs/rGO composite will be used as a high-performance electrode active material,which has great market value in lithium-ion batteries.