The Electrochemical Performance Of Oxygen-deficient Li₄Ti₅O_12-x

Spinel Li4Ti5O12 is a "zero-strain" material, which could ensure superior long cycle life and security during the rapid charging/discharging process. But its inherent low electronic conductivity limits its commercial application.This paper adopted nano ball milling method to mix TiO2 and LiOH·H2O raw materials. The infection of ball milling parameters for the size distribution was investigated. The optimal process parameters was confirmed as follows:the speed is 800r/min, the solid content is 60%, and milling time is 120min. Based on the optimization milling process, the excess lithium source and effect of calcination temperature on the electrochemical properties of the material was ultimately determined with the lithium excess value is 5%, the calcination temperature is 850℃.The infection of different atmosphere for the electrochemical performance was studied based on the optimization synthesis of the precursor. The results demonstrated that different atmosphere has no effect on the crystal structure and morphology of the obtained Li4Ti5O12. The obtained materials calcined under a reducing atmosphere contain part of Ti3+ and oxygen defects, the samples exhibit an excellent electrochemical performance with the initial discharge capacity of 173.1 mAh·g-1 at 0.5C and the lithium ion diffusion coefficient of 4.9*10-12S·cm-2, which is about an order of magnitude higher than the sample calcined in air atmosphere.Li4Ti5O12-x anode powder containing oxygen vacancies was synthesized with graphene oxide as a reducing agent. The main role of graphene oxide and the electrochemical performance of the obtained materials were investigated. The results demonstrated that graphene oxide played the role of reducing agent in promoting the conversion of Ti(IV) into Ti(III) during the calcination process, the process is accompanied by the formation of oxygen vacancies. As a result, the as-prepared Li4Ti5O12-x exhibits excellent electrochemical performance, presenting an initial discharge capacity of 172.4 mAh·g-1 at 0.5C with a capacity retention of 96.7% over 100 cycles.