Preparation And Characterization Of Li₄Ti₅O_12-x/C As Anode Materials For Lithium-Ion Batteries

The spinel Li4Ti5O12has been intensively investigated as a promising anode material for lithium secondary batteries owning to its advantage such as excellent electrochemical properties, good cycling stability, zero-strain properties, low-cost, environmental friendliness and safety for lithium-ion batteries. However, it is very difficult to retain a high capacity and cycling stability at high rates, because its electronic conductivity is very low.In this work, we have suggested solutions to improve the conductivity as follows:(i) particle size minimization;(ii) coating carbon;(iii) generated oxygen vacancies and Ti3+under inert atmosphere. The spinel Li4Ti5O12-x/C nanoparticles were successfully fabricated via wet milling assisted solid-state method with a subsequent Ar treatment. The effects of preparation parameters on the crystalline structure, morphology, performance and Li+intercalation process were studied by X-ray diffraction, scanning electron microscope, cyclic voltammetry, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, electrochemical impedance spectroscopy and charge-discharge experiments.Wet milling assisted solid-state method prepared Li4Ti5O12-x/C with carbon content10%, Li/Ti ratios0.85, sintering temperature750℃, sintering time10h in Ar showed the best electrochemical performance. The resultant Li4Ti5O12-x/C were well indexed to a cubic spinel structure of Li4Ti5O12(space group:Fd3m), and have a uniform size distribution particles within100-200nm. Compared with spinel Li4Ti5O12/C nanoparticles prepared in air, Li4Ti5O12-x/C showed excellent rate performance and cycle ability as represented by discharge capacity of166.2,165.1,163.7,154.8, and140.2mAh·g-1at1C,2C,5C,10C, and20C, respectively. And its capacity retention was99.7%and90.3%after100cycles and500cycles at10C. Along with nanoparticles and carbon-coated, the defective structure with oxygen vacancies and Ti3+significantly improved the disordering of the atoms result in a higher electronic conductivity, lower polarization, and lower charge transfer resistance. Therefore, Li4Ti512-x/C showed a better rate performance and cycle ability than traditional Li4Ti5O12.