Study On The Regulation Of TiO₂-based Micro/Nanostructure And Lithium-ion Battery Performance

Transition metal oxides gradually become one of the hot spots for anode materials for lithium-ion batteries.Among them,the TiO2 negative material has the advantages of safety,environmental friendliness,long cycle life and high rate performance.However,the shortcomings limit the application of TiO2 anode material because its low electronic conductivity,small ion diffusion coefficient,and high electrolyte/electrode interface resistance at high current densities.In this paper,TiO2-based nanomaterial is used as research object to solve these problems,and macroscopic and microscopic structure control is carried out to obtain TiO2-based anode materials with excellent electrochemical performance.Firstly,micron-sized NH4TiOF3 particles self-assembled of nanoparticles were synthesized by hydrothermal method and modified by gas phase to obtain the interface structure with the thin layer of TiO2.Multi-scale structure construction can prevent the agglomeration of nanomaterials.The layered crystal structure of NH4TiOF3 can provide more ion transport channels,further more the special surface/interface structure can improve the conductivity.When the annealing temperature is 250℃,the sample has excellent electrochemical performance that the reversible capacity of 128.6 mAh g-1 is maintained after 2000 cycles at the current density of 1 A g-1.Even,the reversible capacity of 89.6 mAh g-1 is maintained at a high current density of 20 A g-1.Secondly,the TiO2(P25)material was reduced by gas phase to obtain defects of oxygen vacancies and then TiO2 is recombined with the functional group of graphene by spontaneous oxidation-reduction reaction through the defects of oxygen vacancies..The presence of oxygen vacancies can increase the active sites and the conductivity is improved by spontaneous redox reaction form bonds at the defect.The sample annealed at 250℃ under an argon-hydrogen mixed atmosphere then mixed with graphene oxide has the best electrochemical performance.It has the reversible capacity of 258 mAh g-1 after 200 cycles at a current density of 1 C,and still maintains the reversible capacity of 75.5 mAh g-1 at a current density of 50 C.Finally,the oxygen vacancies were generated in the TiO2 by liquid phase reduction of the NaBH4 solution,the effect of NaBH4 solution reduction on the electrochemical performance of TiO2 is not obvious.Then mixed it with the graphene oxide to generate a spontaneous redox reaction.Liquid phase reduction can increases the number of active sites.At the same time,the conductivity is increased due to the bonding of the spontaneous reaction.However,as the concentration of NaBH4 solution increases,the crystallinity of TiO2 decreases.Therefore,it is necessary to strictly control the concentration of the NaBH4 solution.The sample exhibites the best performance when the NaBH4 solution concentration was 1 M.The reversible capacity of 281.3 mAh g-1 is achieved after cycling for 200 cycles at a current density of 1 C,even the reversible capacity of 97.0 mAh g-1 is remained at a current density of 50 C.