Synthesis And Lithium Storage Performances Of Layered Titanate Anode Materials

Lepidocrocite-like layered titanate is considered as an ideal lithium ion battery anode material because of its open and stable layered structure,moderate lithium storage site,easy preparation,pollution-free,and high structural stability.Its special layered structure can provide a large reachable surface area for lithium storage,and more open tunnels,better adaptability to lithium insertion/extraction make it applications an excellent cycle stability for lithium ion battery.However,layered titanate also has problems such as low actual capacity and low first time coulomb efficiency,etc.This is a common problem of titanium-based materials,which makes it insufficient as a practical electrode material.At present,the main solution to the above problem comprises:preparing nano-materials,structure regulating and preparing a composite material etc.The nature of these methods is to improve the structural stability and electrochemical electrode reaction activity of the materials,to improve the lithium storage performance of the electrode.In this paper,in order to study the lithium storage properties of titanates in different interlayer states,K0.8Ti1.73Li0.27O4 is synthesized by hydrothermal method.is synthesized by hydrothermal method firstly,then through protonation and further liquid phase stripping obtined plate-like H1.08Ti1.73O4·H2O and Ti1.73-O41.08+ nanosheets,respectively Compared with KLTO-S synthesized by the solid-phase method,KLTO-H has a larger interlayer distance,higher purity,a more regular layered structure,and a smaller and more uniform particle size,which are conducive to lithium storage.And it can maintain a stable reversible capacity(125mAh·g-1)when cycling for 2000 cycles under a current density of 100 mA·g-1.What's more,the materials obtained by protonation and further liquid phase peeling can maintain good cycle stability in thousands of charge and discharge cycles,and the reversible capacity under different current densities is higher than the corresponding K0.8Ti1.73Li0.27O4 reversible capacity.In view of the low conductivity of titanate materials,a layered titanate was used as the substrate and ?-Bi2O3 with high conductivity was introduced by hydrothermal method to synthesize a sawtooth-like K0.8Ti1.73Li0.27O4/Bi4Ti3O12 composites material.As a negative electrode of lithium ion battery,the composite material shows good capacity reversibility and excellent rate performance.The layered titanate in the composite material reduces the mechanical stress generated during the lithium storage process,and alleviates the structural collapse caused by the stress,more over enhances the structural stability of the composite electrode;besides,bismuth titanate improves the conductivity of the material and makes lithium Ions are easier to insert and extract.On the other hand,this paper explores the lithium storage properties of iron-containing layered titanates.Pure phase K0.8Fe0.8Ti1.2O4 was prepared by hydrothermal method.The effects of hydrothermal temperature and KOH concentration on the synthesis of K0.8Fe0.8Ti1.2O4 were investigated.Comparing of KFTO-S,KFTO-H have a higher purity,more uniform and regular layered structure,and larger specific surface area than those synthesized by solid phase method,which are conducive to meeting the needs of lithium storage reactions.It can maintain a stable reversible capacity(261 mAh·g-1)when it is circulated for 100 cycles at a current density of 100 mA·g-1,which is higher than the reversible capacity of the solid-phase synthesis product(140 mAh·g-1).Further using K0.8Fe0.8Ti1.2O4 as a precursor,H0.8Fe0.8Ti1.2O4 with and higher reactivity was prepared by protonation reaction to investigate its lithium storage performance.In this paper,Fe0.8Ti1.2O48+ nanosheets were prepared by stripping H0.8Fe0.8Ti1.2O4 in the liquid phase.Based on this,Fe2+-doped Fe0.8Ti1.2O48+nanosheets were introduced by UV reduction.Compared with H0.8Fe0.8Ti1.2O4 and Fe0.8Ti.2O48+ nanosheets,Fe2+-doped Fe0.8Ti1,2P48+ nanosheets electrodes has been significantly improved.It's reversible capacity is 180 mAh·g-1 after 2,000 cycles under a current density of 2 A·g-1.The material of the nanosheet structure has a larger specific surface area than the plate-like material,which can provide more active sites for the lithium storage process on the surface of the material,and the introduction of2+ makes the nanosheet conductivity increase.