Synthsis,modification And Electrochemical Performance Of TiO₂ Composite Transition Metal Oxide As Anodes For Lithium-ion Battery

Faced with increasingly serious energy and environmental problems,lithium-ion batteries have been widely used as a secondary battery in recent years.As we all know,the traditional carbon anode material of lithium-ion batteries can no longer meet the social demands of high safety performance and high energy density,because of its low theoretical capacity and the lithium dendrites generated by its low-voltage platform.Based on the many issues,developing of anode materials with high capacity and high safety performance is one of the efficacious strategies to enhance the performance of lithium ion batteries.The transition metal oxide has been widely studied due to the high theoretical capacity,however the application has been limited by the volume expansion problem during charging and discharging.Among them,titanium dioxide?TiO₂?that with a low volume expansion and has good cycle stability is a potential anode electrode material because redox reactions are absent during charge/discharge process.In this study,synthesis of TiO₂ and other metal oxide composite nano-block Li₄Ti₅O₁₂/TiO₂,porous spherical Co₃O₄/TiO₂ and MnCo₂O₄/TiO₂,two-phase materials were synthesized to improve the safety performance,cycle stability performance and reversible capacity of materials.The main research contents are summarized as follows:?1?A dual-phase Li₄Ti₅O₁₂/TiO₂?LTO/TO?was synthesized by a simple solvothermal method using only lithium hydroxide monohydrate and tetrabutyl titanate as reagents,and the tetrabutyl titanate was hydrolyzed by lithium hydroxide crystal water under high temperature and pressure conditions.This experiment shows that the cycling performance and rate performance of lithium titanate can been effectively improved by the incorporation of titanium dioxide.The LTO/TO composites electrode exhibited excellent electrochemical performance.The nanostructured two-phase LTO/TO composites can shorten the diffusion of electrons and lithium ions distance.This simple synthesis method is feasible and can be applied to the synthesis of other similar electrode materials.?2?Hollow spherical Co₃O₄ was prepared by a liquid precipitation method,and a two-phase Co₃O₄/TiO₂ material was successfully synthesized by the hydrolysis of tetrabutyl titanate to form a layer of TiO₂ coating on its surface.This hollow spherical Co₃O₄ is made up of particles with a diameter of about 50 nm.The porous structure can not only effectively shorten the lithium ion transmission path,but also fully infiltrate the electrolyte and electrode materials,providing more reactive sites point.The test results show that the prepared Co₃O₄/TiO₂material exhibited excellent lithium storage performance,delivering a discharge capacity of1090 mAh g^-1 after 300 cycles at a current density of 0.2 A g^-1,while the discharge capacity of the pure phase Co₃O₄ battery is 450 mAh g^-1.The results indicated the recombination of TiO₂ greatly improves the cycle performance of Co₃O₄.?3?Based on the results of the previous chapter,Co were replace by Mn which can further increased the structural stability of the material in this chapter.A binary metal oxide MnCo₂O₄with a porous structure was successfully prepared by a simple liquid-phase precipitation method,and the MnCo₂O₄@TiO₂ composites were synthesized finally.From the results of the electrochemical performance tests,it can be seen that TiO2 coating effectively improves the cycle stability of the electrode material.