Study On Preparation And Electrochemical Performance Of Li₄Ti₅O₁₂ As Anode Materials For Lithium Ion Batteries

As an anode material for lithium ion batteries (LIBs), spinel lithium titanate(Li4Ti5O12) exhibits negligible volume change during Li+insert-desert processe, so itwas named as zero-strain material. Furthermore, spinel Li4Ti5O12has been regarded asone of promising anode material, because it has outstanding cycle reversibility, highsafety and environmental friendliness. The low electrical and ionic conductivity ofLi4Ti5O12material give rise to poor high rate capability, however, that hinders itscommercial application.In order to overcome the serious drawback, some strategies (as follows) havebeen applied to improve the high rate capability of Li4Ti5O12material, includingenhancement of its electric conductivity by surface coating with a more conductivematerial, and/or doping with foreign atoms.1. Li4Ti5O12-TiO2composite has been prepared through a solid-state method, andelectrochemical performances of materials were investigated. The result shows thatTiO2can enhance the electric conductivity of Li4Ti5O12, which can improveelectrochemical performances of the composite. When Li/Ti molar ratio is4.5:5, theelectrode still retains an outstanding reversible discharge capacity of168.2mAh g-1after900cycles at1C at room temperature. Furthermore, the electrode exhibitsexcellent discharge capacity of155mAh g-1at the500th cycle at55℃.2. Li4Ti5O12@CeO2composite has been synthesized through a co-precipitationmethod. After systematical tests, it is found that CeO2is successfully coated on thesurface of Li4Ti5O12material, besides partial doping of Ce4+into the Li4Ti5O12structure. The composite shows the best electrochemical performance whenCe4+/Li4Ti5O12molar ratio is0.05. It exhibits excellent discharge capacity of152mAhg-1after180cycles at10C, with no noticeable capacity fading. In addition, thecomposite can deliver a discharge capacity of128.4mAh g-1at40C, which is much higher than pure Li4Ti5O12material.3. Li4Ti5-x(PO4)xO12-4x(0≤x≤0.05) has been synthesized by a co-precipitationmethod. When x=0.01, there are no impurity phases detected in the XRD patterns.Furthermore, the electrode presents better electrochemical performance than theLi4Ti5O12material prepared by the similar process. The electrode exhibits an excellentcycling stability with a discharge capacity of157mAh g-1at10C after500cycles.Remarkably, the electrode can deliver a specific capacity of126.3mAh g-1at40C.The results demonstrate phosphate doped Li4Ti5O12reduces polarization of Li4Ti5O12,besides enhances Li+diffusion coefficient and facilitates the charge transfer reactionsduring charge/discharge process.