Effect of rich R-TiO2 on the rate and cycle properties of Li4Ti5O12 as anode for lithium ion batteries

Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement of X-ray diffraction (XRD) results show that the proportion of Li occupying 16d sites is extraordinary low and the lattice constants of LTO and R-TiO2 change with the ritanium dioxide content. EIS measurements showed that with in creasing R-TiO2 content, both its charge transfer impedance (Rct) and lithium ion diffusion coefficient (DLi) decreased. The changes of Rct and DLi caused by the increase of titanium dioxide content have synergic-antagonistic effects on the rate and cycle properties of Li4Ti5012. The rate performance is positively related to DLi, while the cycle property is negatively correlated with Rct, indicati ng that the rate performs nee is mainly related to DLi, while Rct more significantly affects the cycle performance. LTO-RT-17.06% exhibited excellent rate properties, especially under a high current density (5.0 C, 132.5 mAh/g) and LTO-RT-34.42% showed superior long-term cycle performance (0.012% capacity loss per cycle) compared to that of LTO-RT-17.06% and LTO-RT-23.69%.

锌掺杂对Li_4Ti_5O_(12)负极材料电化学性能的影响

通过溶胶凝胶法制备Li4Ti5O12及锌掺杂Li4-2x/3ZnxTi5-x/3O12(x=0.05,0.10,0.15,0.20)活性材料,并优化了最佳掺杂量为x=0.10。通过X射线衍射(XRD)、扫描电镜(SEM)、恒流充放电测试对材料进行结构、形貌及电化学性能表征。结果表明:掺杂适量的锌离子不会改变钛酸锂的尖晶石结构和形貌,1C时,Li3.93Zn0.10Ti4.97O12放电比容量升高且容量保持率为99.74%;而纯相的容量保持率仅为94.30%。

Significant effect of electron transfer between current collector and active material on high rate performance of Li_4Ti_5O_(12)

The rate and cycling performances of the electrode materials are affected by many factors in a practical complicated electrode process. Learning about the limiting step in a practical electrochemical reaction is very important to effectively improve the electrochemical performances of the electrode materials. Li4Ti5O12, as a zero-strain material, has been considered as a promising anode material for long life Li-ion batteries. In this study, our results show that the Li4Ti5O12 pasted on Cu or graphite felt current collector exhibits unexpectedly higher rate performance than on A1 current collector. For Li4Ti5O12, the electron transfer between current collector and active material is the critical factor that affects its rate and cycling performances.

Preparation and characterization of SnO_2-Li_4Ti_5O_(12) composite by sol-gel technique

SnO2-Li4Ti5O12 was prepared by sol-gel method using tin tetrachloride,lithium acetate,tetrabutylorthotitanate and aqueous ammonia as starting materials.The composite was characterized by thermogravimertric(TG)analysis and differential thermal analysis(DTA),X-ray diffractometry(XRD)and transmission electron microscopy(TEM)combined with electrochemical tests.The results show that SnO2-Li4Ti5O12 composite derived by sol-gel technique is a nanocomposite with core-shell structure, and the amorphous Li4Ti5O12 layer with 20?40 nm in thickness is coated on the surface of SnO2 particles.Electrochemical tests show that SnO2-Li4Ti5O12 composite delivers a reversible capacity of 688.7 mA·h/g at 0.1C and 93.4%of that is retained after 60 cycles at 0.2C.The amorphous Li4Ti5O12 in composite can accommodate the volume change of SnO2 electrode and prevent the small and active Sn particles from aggregating into larger and inactive Sn clusters during the cycling effectively,and enhance the cycling stability of SnO2 electrode significantly.

Synthesis and electrochemical properties of LiMn_2O_4/Li_4Ti_5O_(12) composite

LiMn2O4/Li4Ti5O12 composite was synthesized by in-situ composite technique using LiMn2O4,lithium acetate,tetrabutyl titanate as starting materials and characterized by various electrochemical methods in combination with X-ray diffractometry(XRD), infrared(IR)spectroscopy and scanning electron microscopy(SEM).The results show that Li4Ti5O12 is coated on the surface of crystalline LiMn2O4 to form LiMn2O4/Li4Ti5O12 composite.The structure of LiMn2O4 does not change due to the introduction of Li4Ti5O12.By being coated with Li4Ti5O12,the rate capability and high temperature cyclability of LiMn2O4 is improved greatly.At room temperature,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 108.4 mA·h/g and the capacity loss per cycle is only 0.053%after 20 cycles at 2.0C.While at 55℃,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 109.9 mA·h/g and the capacity loss per cycle is only 0.036%after 60 cycles at 1.0C.

Preparation of Li4TisO12 Microspheres with a Pure Cr2O3 Coating Layer and its Effect for Lithium Storage

The pure Cr2O3 coated Li4Ti5O12 microspheres were prepared by a facile and cheap solution- based method with basic chromium（III） nitrate solution （pH=ll.9）. And their Li-storage properties were investigated as anode materials for lithium rechargeable batteries. The pure Cr2O3 works as an adhesive interface to strengthen the connections between Li4Ti5O12 par- ticles, providing more electric conduction channels, and reduce the inter-particle resistance. Moreover, Li2Cr2O3, formed by the lithiation of Cr2O3, can further stabilize LiTTi5O12 with high electric conductivity on the surface of particles. While in the acid chromium solution （pH=3.2） modification, besides Cr2O3, Li2CrO4 and TiO2 phases were also found in the final product. Li2CrO4 is toxic and the presence of TiO2 is not welcome to im- prove the electrochemical performance of Li4Ti5O12 microspheres. The reversible capacity of 1% Cr2O3-coated sample with the basic chromium solution modification was 180 mAh/g at 0.1 C, and 134 mAh/g at 10 C. Moreover, it was even as high as 127 mAh/g at 5 C after 600 cycles. At -20 ℃, its reversible specific capacity was still as high as 118 mAh/g.

Preparation of Li_4Ti_5O_(12) submicrospheres and their application as anode materials of rechargeable lithium-ion batteries

We report on the preparation of spinel Li4Ti5O12 submicrospheres and their application as anode materials of rechargeable lithium-ion batteries. The spinel Li4Ti5O12 submicrospheres are synthesized with three steps of the hydrolysis of TiCl4 to form rutile TiO2, the hydrothermal treatment of rutile TiO2 with LiOH to prepare an intermediate phase of LiTi2O4+δ, and the calcinations of LiTi2O4+δ to obtain spinel Li4Ti5O12. The as-prepared products are investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The diameters of Li4Ti5O12 submicrospheres with novel hierarchical microstructures are about 200–300 nm with the assembly of 20–30 nm nanoparticles. The electrochemical properties of Li4Ti5O12 submicrospheres are measured by galvanostatical discharge/charge test and cyclic voltammetry (CV). The as-prepared Li4Ti5O12 display excellent discharge/charge rate and cycling capability. A high discharge capacity of 174.3 mAh/g is obtained in the first discharge at 1 C rate. Meanwhile, there is only tiny capacity fading with nearly 100% columbic efficiency in the sequential 5–50 cycles. Moreover, lithium-ion diffusion coefficient in Li4Ti5O12 is calculated to be 1.03 × 10-7 cm2/s. The present results indicate that the as-prepared Li4Ti5O12 submicrospheres are promising anode candidates of rechargeable Li-ion batteries for high-power applications.

Sol-gel Synthesis and Electrochemical Performance of Li4-xMgxTi5-xZrxO12 Anode Material for Lithium-ion Batteries

The anode materials Li4-xMgxTi5-xZrxO12（x=0, 0.05, 0.1） were successfully synthesized by sol-gel method using Ti（OCaH9）4, CH3COOLi·2H2O, MgCl2·6H2O and Zr（NO3）3·6H2O as raw materials. The crystalline structure, morphology and electrochemical properties of the as-prepared materials were characterized by XRD, SEM, cyclic voltammograms （CV）, electrochemical impedance spectroscopy （EIS） and charge-discharge cycling tests. The re- sults show that the lattice parameters of the Mg-Zr doped samples are slightly larger than that of the pure LiaTi5Oi2, and Mg-Zr doping does not change the basic Li4Ti5O2 structure. The rate capability of Li4-xMgxTi5-xZrxO12 （x= 0.05, 0.1） electrodes is significantly improved due to the expansile Li＋ diffusion channel and reduced charge transfer resistance. In this study, Li3.95Mg0.05Ti4.95Zr0.05O12 represented a relatively good rate capability and cycling stability, after 400 cycles at 10 C, the discharge capacity retained as 134.74 mAh·g-1 with capacity retention close to 100%. The excellent rate capability and good cycling performance make Li3.95Mg0.05Ti4.95Zr0.05O12 a promising anode material in lithium-ion batteries.