Preparation Of TiO₂ Composites And Study Of Their Lithium Storage Properties

At present,commercial lithium-ion batteries have great safety hazards,such as new energy vehicles often have battery spontaneous combustion or explosion and other safety problems.Therefore,there is a need for batteries with safer,higher reversible ratio capacity,better cycle stability and multiplier performance.Among many lithium-ion battery electrode material solutions,TiO₂-based cathode material becomes a good choice,which has many unique advantages,such as:during the cycle process,due to the high lithium-embedded voltage,so it is hard to occur lithium plating and the battery safety performance is good.During cycling embedding/detachment of lithium ions,TiO₂-based cathode material has a stable crystal structure,which can effectively suppress the problem of electrode expansion or detachment.However,TiO₂ anode materials still suffer from some shortcomings,such as low actual lithium ion diffusion coefficient and poor electrical conductivity.In order to overcome these deficiencies and to prepare TiO₂-based anode materials with high safety performance,excellent multiplicity performance,reliable cycle stability and high specific capacity,this thesis has modified TiO₂-based anode materials in three aspects.Firstly,the titanium-based oxide is compounded with the conductive carbon material,reduced graphene oxide.The reduced graphene oxide sheet layer can provide TiO₂ with stable and fast ion transport kinetics and a highly conductive layer during the embedding/de-embedding of lithium ions,which can effectively improve the inherent poor electrical conductivity of TiO₂.In addition,by comparing the effects of two different crystalline types of titanium dioxide on the battery performance,the a-TiO₂ shell layer has lower lithium ion diffusion resistance,higher specific capacity and better multiplicative performance.The composite r GO@a-TiO₂showed an excellent specific capacity of 218 m Ah g^-1 after 2500 cycles at 1 A g^-1 and 97m Ah g^-1 after 5000 cycles at 3 A g^-1 as an anode for Li-ion batteries.Next,an ultrathin graphene cube structure is constructed and compounded with a-TiO₂ to obtain a Gr@a-TiO₂ composite anode.The ultra-thin graphene cube framework can enhance the ion transport kinetics and conductivity of a-TiO₂ during lithiation/delithiation and provide a strategic layer with low electrode expansion.The optimised Gr@a-TiO₂ shows an excellent specific capacity of 179.4 m Ah g^-1 after 4000 cycles at 1 A g^-1 and 97.2 m Ah g^-1after 3000 cycles at 5 A g^-1.Finally,to enhance the overall specific capacity and mass density of the titanium-based anode material,in combination with rod-shaped Mn O₂ and through the successful plasma The whole structure of Mn O_x@a-TiO_y improves the electrochemical performance,achieving stable cycling and activating an increased capacity to sustain long-term cycling(specific capacity of 829.6 m Ah g^-1 after 2000cycles at 1 A g^-1 current density),with a significant increase in multiplicative performance and specific capacity.And as a buffer layer,the a-TiO₂,modified coating layer,can effectively release the stress/strain of the active material during lithiation/delithiation,providing excellent electrode level integrity.