Study On Preparation And Electrochemical Performance Of Titanium Oxide With High Rate Performance

Spinel Lithium titanate(Li₄Ti₅O₁₂,LTO)materials with"zero strain"characteristics as anodic materials for lithium-ion batteries poesses outstanding characteristics such as long cycling life,excellent high-rate performance and wide working temperature.Moreover,the charging-discharging voltage platform of LTO is high（～1.55 V vs.Li⁺/Li）,which can effectively avoid the formation of solid electrolyte membrane and lithium dendrite.As a result,LTO batteries have wide application prospect in hybrid electric vehicles,new energy public transport and energy storage technology.However,the poor electronic and ionic conduction of LTO materials limit their high-rate performances.Therefore,structural optimization of LTO is a research hotspot to improve its electrochemical performance.In this paper,commercial titanium dioxide（P25,TiO₂）and lithium hydroxide（Li OH·H₂O）were used as titanium sources and lithium sources,respectively,the two-step hydrothermal method and further calcination method were used to prepare the LTO material with a hierarchical structure.The preparation process was optimized,and the LTO materials were modified further by ion doping.The microstructure and electrochemical properties of the prepared LTO materials were studied by X-ray diffraction,scanning electron microscopy and constant current charging-discharging methods.The results showed that the pure phase precursor（H₂Ti₂O₅·2H₂O）can be obtained by using ammonium chloride solution as ion replacement material,and pure LTO with hierarchical structure can be obtained under different tempretures when the molar ratio of lithium to titanium was 1:1.LTO materials calcined at 600℃for 2 h,exhibit high purity and small primary particle size,and thus exhibit excellent high-rate and cycling performances.Their specific capacities were 148 mAh·g^-1at 1 C.When the current density reaches 60 C,the specific capacity was still up to 123 mAh·g^-1.Meantime,the capacity retentions were 90.1%and 88.1%after 500 cycles at 20 C and50 C,respectively.Fluorine-doped LTO700 material was prepared by mechanical mixing and further low temperature calcination,and the electrochemical properties of were discussed.The results showed that F-doping greatly improves the electrochemical performance of the LTO700.F-LTO with the doping amount of 5 wt.%had good electrochemical performance.The specific capacities of the material at 1 C、5 C、10 C、20 C、30 C、40 C、50 C、60 C and 70 C were 149,136,131,124,119,108,103 and 98 mAh·g^-1,respectively.The specific capacity is still up to 134 mAh·g^-1after 500 cycles at 5 C,and the capacity retention is 98.5%,which demonstrates excellent high-rate performance and cycling stability.