Preparation Of Metal Oxide Composite Lithium Titanate And Research On Its Lithium Storage Performanc

Li₄Ti₅O₁₂ with a spinel structure is considered one of the most promising anode materials for lithium-ion batteries.However,Li₄Ti₅O₁₂ suffers from issues such as low capacity and poor cycling performance.Therefore,many researchers have employed the method of oxide composite modification for Li₄Ti₅O₁₂.In this study,different metal oxide-composite Li₄Ti₅O₁₂ materials were prepared using high-temperature solid-state synthesis,and the changes in the electrochemical performance of the composite materials were investigated.Many researchers have utilized hydrothermal and sol-gel methods to prepare Li₄Ti₅O₁₂-TiO₂ materials with the aim of improving the performance of the materials.However,in the solid-state preparation of Li₄Ti₅O₁₂,researchers consider residual TiO₂ as an impurity that can degrade the performance of lithium titanate.Therefore,in order to determine the true role of TiO₂ in the solid-state preparation,this study employed the high-temperature solid-state synthesis method to prepare TiO₂ composite materials with different contents and crystal structures under air and argon atmospheres.When the Li₂CO₃ content was 100%,the prepared composite materials exhibited diffraction peaks corresponding to rutile TiO₂.When the Li₂CO₃ content was reduced to 90%,the prepared materials showed diffraction peaks of anatase TiO₂.To investigate the factors influencing the phase transition,the anatase TiO₂ was sintered under different atmospheres,and the XRD results showed that all the prepared materials were of anatase TiO₂ phase.Based on the XRD results of materials prepared under different atmospheres,it was found that Li₂CO₃ could promote the transformation of anatase TiO₂ to rutile TiO₂,and the argon atmosphere had a higher TiO₂ transformation rate compared to the air atmosphere.SEM analysis of L85-Ar revealed a reduction in particle size,and the presence of rutile and anatase TiO₂ was confirmed through lattice fringes,element distribution,and selected-area electron diffraction.Electrochemical tests demonstrated that Li₄Ti₅O₁₂-TiO₂ reduced the low-rate performance of the material while enhancing the high-rate performance and long cycling performance of the modified composite material.Continuing the strategy of metal oxide modification of lithium titanium,attempts were made to prepare Mo⁴⁺doped Li₄Ti₅O₁₂ and Li₄Ti₅O₁₂-MoO₂ composite modified materials.MoO₂ material was prepared by high-temperature reduction of Mo O₃ under a reducing atmosphere.XRD analysis confirmed the formation of MoO₂ from Mo O₃ after sintering at650°C under a reducing atmosphere.SEM analysis revealed that the prepared MoO₂consisted of rod-shaped particles with sizes in the tens of micrometers.Using the reduced MoO₂ as a raw material,Mo⁴⁺doped Li₄Ti₅O₁₂ material was synthesized.However,due to surface oxidation of the MoO₂ material,its rate performance was poor in electrochemical testing.To avoid material oxidation,another approach was adopted to prepare the Li₄Ti₅O₁₂-MoO₂ material.In the composite material,as the MoO₂ content increased,the initial discharge capacity of the material first increased and then decreased,with a maximum initial discharge capacity of 187 m Ah/g,exceeding the theoretical capacity of Li₄Ti₅O₁₂.This was attributed to the participation of MoO₂ in the initial discharge process in the composite material.However,due to the relatively large particle size of the prepared MoO₂,the high-rate capacity of the physically modified material decreased due to issues such as volume expansion and particle.