Synthesis And Performance Of Anatase Titanium Dioxide Anode Materials For Sodium Ion Batteries

Nowadays,lithium ion batteries have been widely used in power battery systems and portable electronic devices due to its advantages of high energy density,long cycle life,environmental friendly,etc.But with the development of the electric car industry,the growing demands for lithium ion batteries have required to ensure sufficient source of lithium.We have to face uneven geographically distribution of lithium?70%in South America?,which may lead to the resources shortage problems and continuously prices raising.So developing suitable substitute products for lithium ion batteries becomes an urgent task.As sodium and lithium are in the same group,sodium also has not only many properties similar to lithium,but also many unique advantages of abundance,low price,and environmental friendly.Thus,sodium ion batteries are potential substitute for lithium ion batteries.There are many researchs on cathode materials for sodium ion batteries,on contract,researches on anode materials is relatively less.At present,the study on anode materials for sodium ion batteries mainly focus on:carbon based materials,titanium based materials,alloy anode materials,organic anode materials,etc.Among them,titanium dioxide?TiO₂?materials with low cost,good stability and long cycle life have attracted much more attention in recent years.In this work,commercial TiO₂ samples with different crystalline structure?anatase and rutile?were investigated as anode materials in sodium ion batteries.We find that anatase TiO₂ is more suitable for sodium storage since its reversible capacity?84.6 mAh/g,100 mA/g?is nearly twice of that of rutile TiO₂?43.1 mAh/g,100mA/g?.We further modify the TiO₂ nanoparticles by coating with reduced graphene oxide?RGO?using spray-drying method combined with heat treating.The coating of RGO can greatly improve the electrochemical performance of TiO₂ materials in sodium ion batteries due to the increased electrical conductivity.The TiO₂/RGO?4.0%?w??composites exhibited good cycle stability?146.7 mAh/g,100 mA/g,after 350 cycles?and excellent rate capabilities?114.4 mAh/g,600 mA/g?.To synthesize TiO₂ nanoparticles with enhanced performance,we use different raw materials through different methods to prepare a serious of TiO₂ samples.The crystal structure,micromorphology and electrochemical properties of the prepared samples were studied and compared.FSEM observation indicated that TiO₂ materials synthesized through different methods showed great difference in microscopic morphology and crystal structure.We found out that TiOSO₄ is a preferable raw material with low price,which can be used to synthesize anatase TiO₂ by hydrothermal method.This prepared TiO₂ product showed uniform particle size distribution,with average particle size around 20⁵0 nm,which exhibited good reversible capacities of 172.5 mAh/g?20 mA/g?,124.2 mAh/g?100mA/g?and well cycle stability.On this basis,we chose cetyltrimethylammonium bromide?CTAB?as a surfactant and TiOSO₄ as raw material to synthesize a series of TiO₂ samples by template hydrothermal method.We also optimized the hydrothermal method to obtain anatase TiO₂ materials with better electrochemical performance.Electrochemical test results showed that the prepared TiO₂ materials exhibited reversible capacities of 241.9 mAh/g?20 mA/g?and 179.6mAh/g?100 mAh/g?,which showed much better electrochemical performance compared with the commercial anatase TiO₂ materials.