Synthesis,Modification And Electrochemical Properties Of Hollow Nanostructure TiO₂ Electrode Materials

Lithium-ion batteries?LIBs?have received extensive attention due to their high capacity,long cycle life,and environmental friendliness,and have been used in portable electronic devices and electronic vehicles.Titanium dioxide?TiO₂?has been deeply studied due to its advantages of low price,non-toxicity,structural stability,and high safety.However,the low electronic and ionic conductivity of TiO₂ limits its application in the field of LIBs.Therefore,it is imminent to synthesize TiO₂ with nano-scale structure or composite TiO₂ with conductive carbon materials,metal materials,metal oxide materials to improve its defects.In this paper,TiO₂ with hollow nano-structured was prepared by hydrothermal method.On this basis,the composite was prepared by combining with reduced graphene oxide?RGO?and carbon nanotubes?CNTs?respectively.The obtained materials were characterized by XRD,SEM,TEM and other test techniques.Then it were used as anode materials for lithium ion batteries?LIBs?to perform cyclic voltammetry,charge-discharge,electrochemical impedance spectra and other tests to study the electrochemical properties of the material.The main research contents and results of this paper are as follows:?1?The influence of the experimental factors on the electrochemical properties of the hollow nanostructure TiO₂ was studied by using the control variable method to study the effects of hydrothermal time,hydrothermal temperature,lithium hydroxide dosage and calcining temperature during the experiment.The characterization and electrochemical performance test results show that when the dosage of lithium hydroxide,the hydrothermal time,the hydrothermal temperature and the calcining temperature are 5g,2 d,130°C and 450°C,respectively,the sample delivers a distinct morphology with uniform grain size,high crystallinity and unique hollow nanostructures.At a current density of 0.5 C,the initial discharge specific capacity TiO₂ with hollow nanostructure reaches 570 m Ah g^-1,and the reversible specific capacity reaches 223 mAh g^-11 after 100cycles.?2?A one-step hydrothermal method was adopted to compound RGO and the TiO₂with the hollow nanostructure.After hydrothermal and calcination treatment,the TiO₂with good dispersibility and uniform particle distribution still retained hollow nanosphere structure and uniformly loaded on the RGO.The nanocomposite TiO₂@RGO was obtained by doping different mass of RGO,and the composite showed the best electrochemical performance when doped with 50 mg RGO.When the current density is0.5 C,the discharge capacity of the first cycle is 633.5 mAh g^-1,and the current capacity remains at 352 mAh g^-1after 100 cycles.After cycling at high current density of 10 C for2000 cycles,the specific capacity still remains 217 mAh g^-1.The capacities of other RGO-doped composites were all higher than that of TiO₂ for 223 mAh g^-1at current density of 0.5 C and 135.5 mAh g^-11 for 2000 cycles at current density of 10 C.Experiments show that the composite of TiO₂ and RGO can significantly improve the electrochemical performance of TiO₂.?3?One-step hydrothermal method was used to prepare TiO₂ and TiO₂@CNTs nanocomposites with only by using tetrabutyl titanate?TBT?,carbon nanotubes,and lithium hydroxide as raw materials without adding a dispersant.Compared with the materials before and after compounding,the size of TiO₂ became smaller and the specific surface area increased,but the hollow nanostructure of TiO₂ did not change.By adding different masses of CNTs,combining with characterization techniques,it was found that TiO₂@CNTs composites exhibited the best electrochemical performance when doped with 25 mg CNTs.The specific discharge capacity was 335.5 m Ah g^-11 when TiO₂@CNTs-25 circulated at a current density of 0.5 C for 100 cycles,and the average cycle efficiency lost only 0.329%.When the current density was increased to 10 C,the discharge specific capacity was 223.8 mAh g^-1after 2000 cycles of TiO₂@CNTs-25,the discharge specific capacity was still 165 mAh g^-11 after 6000 cycles.It demonstrates that the composite electrode material has high stability.Experiments show that the addition of CNTs will effectively improve the electrochemical performance of TiO₂ as anode electrode material for lithium-ion batteries.