The TiO₂ Nanostructure Synthesis And Electrochemical Performances Study Of Anode Materials For Lithium-ion Battery

Among various energy storage and conversion devices,lithium-ion batteries(LIBs)are considered as the most important research object for sustainable development,in which anode materials play a key role in determining the electrochemical performance of the battery.Although graphite is currently the most widely used anode,huge challenges are remained in terms of the low capacity,poor rate performance and lithium dendrite growth at fast charge process.Titanium dioxide,a typical insertion-type anode,is considered as a promising anode for next-generation LIBs due to its low cost,high stability and environment-friendly.However,poor conductivity and low ionic conductivity severely hinder the application as anode material.Hence,this thesis focused on designing nano-scale structure,carbon-coating and surface treatment to improve the electrochemical performance as anode for LIBs.The research work includes the following parts:1.a scalable and facile strategy based on sacrificial template-accelerated hydrolysis and polydopamine coating is proposed to manufacture uniform N-doped carbon-coated Ti O₂hollow spheres.The nanostructured hollow structure can shorten the path of Li⁺insertion/extraction in electrode material and increase the contact area between electrode and electrolyte.More importantly,the uniform carbon layer can improve the electronic conductivity.The Ti O₂@C material achieves reversible average capacity of 390.2 m Ah g^-1 at current density 0.1 A g^-1.Besides,even at a high rate of 5.0 A g^-1,Ti O₂@C anode can deliver a high reversible capacity of 166.3 m Ah g^-1 after 2000 cycles with 99.6%capacity retention rate.2.Sulfated titania hollow nanospheres were successfully prepared by a universal and simple acid impregnation method.Benefiting from the formation of a stable functionalized modified layer on the surface forms a stable solid electrolyte interface.The surface modification can provide more lithium-intercalation active sites on the surface and a rapid diffusion channel for lithium ions,and the contribution of pseudocapacitance is improved at a high scan rate.Therefore,the Ti O₂/SO₄^2-electrode provides excellent discharge capacity of360.4 m Ah g^-1 at 0.1 A g^-1,and even at a current rate of 5.0 A g^-1,the Ti O₂/SO₄^2-electrode retains a high capacity of 156.3 m Ah g^-1 over 1500 cycles.In conclusion,this thesis puts forward new insights to design high-performance and long-cycle stable titanium dioxide LIBs anode materials.