Study On Synthesis And Electrochemical Performance Of TiO₂ Composite Anode Materials

TiO2 has been studied consumingly in recent years for its outstanding properties like,minimal toxicity,low cost,nonpollution,high discharge potential and most importantly inherent chemical stability.Nevertheless,the widespread practical application of TiO2 as anodes in lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)is seriously impeded by its inferior rate performance resulting from both extremely poor and electronic conductivity,the huge band gap and sluggish lithium ion diffusion.This thesis is focused on improving the electronic conductivity and electrochemical performance of TiO2.First,the anatase TiO2/TiO2(B)electrode material with hybrid crystal has been synthesized and the anatase TiO2/TiO2(B)was doped with Ti3+ and coated with carbon.Second,the TiO2(B)with special morphology has been prepared and coated with MoS2.The dark Ti3+-doped anatase TiO2@C composite spheres(TD-TiO2@C)were synthesized by the solvothermal.The glycerol and alcohol mixed solvent works as reductant.A series of physical characterization have been operated,in order to discuss the synergic effects of carbon coating and Ti3+ doping on the properties of titanium dioxide.The Ti3+ can improve the electrical conductivity,and carbon layer also can enhance the electronic conductivity.The synergic effects of carbon coating and Ti3+doping make the TD-TiO2@C as lithium ion battery anode materials have excellent electrochemical performance.TD-TiO2@C spheres exhibit excellent electrochemical performance as anode materials for lithium ion batteries.The electrodes not only exhibit a superior capacity of 244.80 mAh g-1 at 1 C(0.168 A g-1)after 100 cycles,but also show an eminent rate capability.TD-TiO2@C spheres retain discharge capacities of 171.78,143.45,119.17,105.82 mAh g-1after 500 cycles at 5 C,10 C,20 C,30 C,holding a capacity retention of as high as 91.0%,84.2%,82.1%,82.0% when compared with discharge capacities at the 10 th cycle,respectively.The linear TiO2(B)/MoS2 composites have been successfully synthesized via facile hydrothermal method.The layer structure of MoS2 is similar to graphite,with a strong in-plane and a weak out-of-plane bondings.Moreover,MoS2 has a larger interlayer spacing than graphite,which can offer a wide range of electron affinity for the intercalation of sodium ions,so MoS2 possesses the high specific capacities and superior conductivity.In addition,the morphology of linear also has certain influenceon the capacity of the composite materials.The electrodes exhibit a superior capacity of 378.5 mAh g-1at 1 C in the first time discharge,after 100 cycles,also retain discharge capacities of 160.1 mAh g-1.Its performance is much better than the pure TiO2(B),and show an eminent rate capability.The TiO2(B)/MoS2 retain discharge capacities of 214,173,138,106,77 mAh g-1at 1 C,2 C,5 C,10 C,20 C,when the current density raise to 1 C,TiO2(B)/MoS2 shows a reversible capacity of 200 mAh g-1.