Li4Ti5O12 TiO2 Research Articles

Hierarchical carambola-like Li4Ti5O12-TiO2 composites as advanced anode materials for lithium-ion batteries

Hierarchically structured Li4Ti5O12-TiO2 (LTO-TiO2) composites are synthesized using a facile hydrothermal approach upon reaction time control. With control over the time of hydrothermal reaction at 18h, a hierarchical dual-phase LTO-TiO2 composite with appropriate amount of anatase TiO2 can be obtained, and it possesses a uniform carambola-like framework assembled by numerous ultrathin nanosheets, which enable a relatively large specific surface area, along with abundant interlayer channels to favor electrolyte penetration. When used as anode materials for lithium-ion batteries, such carambola-like LTO-TiO2 composite exhibits remarkably improved capacity, high-rate capability, and cycling stability over other LTO-TiO2 samples, which are synthesized at different time of hydrothermal reaction. Specifically, it deliveries a discharge capacity as high as 115.1 and 91.2mAhg−1at a very high current rate of 20 and 40C, respectively, while a stable reversible capacity of 171.7mAhg−1 can be retained after 200 charge-discharge cycles at 1C, corresponding to 88.6% capacity retention. The excellent electrochemical performances benefit from the unique hierarchical carambola-like structure together with the mutually complementary intrinsic advantages between LTO and TiO2. The robust and porous nanosheets-assembled LTO-TiO2 framework not only offers a shorter transport pathway for electron and Li-ion migration within this composite material, but also is able to alleviate the structure distortion during the fast Li-ion insertion/extraction process. The work described here shows that the hierarchical carambola-like LTO-TiO2 composite is a promising anode material for high-power and long-life lithium-ion batteries.

Ellipsoid-like Li4Ti5O12–TiO2 composites constructed by nanocrystals for lithium ion batteries

Porous ellipsoid-like Li4Ti5O12–TiO2 composites with a unique micro/nano structure have been successfully fabricated via a facile sol–gel route followed by calcination.

Conductivity Enhancement and Thin-Film Processing of Li4Ti5O12(LTO) Spinel for Li Battery Applications

Spinel Li4Ti5O12 has been considered as one of the most prospective anode materials for Li-ion microbatteries. Homogeneous and crack-free Li4Ti5O12 film with thickness around 200 nm have been deposited on Pt/Ti/SiO2/Si(100) substrate by r.f. magnetron sputtering. The influence of the post-annealing treatment on the phase composition, structure and electrochemical behavior was studied. The Li/Ti molar ratio in the films decreased with an increasing oxygen fraction. The amount of Li4Ti5O12 phase increases with the annealing temperature increasing from 500°C to 700°C. Electrochemical characterization of samples treated at 600°C presents a redox reaction around 1.55 V indicating that the film contains Li4Ti5O12 spinel. Larger capacity and good reversibility in the sample post-annealing treatment at 600 °C can be attributed to high crystallinity of Li4Ti5O12 and amorphous TiO2 phase.

Synthesis of Nanoporous Li4Ti5O12–TiO2 Composites for High‐Performance Lithium‐Ion‐Battery Anodes

AbstractThis work reports the synthesis of Li4Ti5O12–TiO2 nanoporous composites through an effective, inexpensive, and easily scalable approach. The as‐synthesized products were calcined under a nitrogen atmosphere at 700, 750, or 800 °C. When used as anode materials for lithium‐ion batteries, the 750 °C nitrogen‐treated Li4Ti5O12–TiO2 sample showed significantly improved capacity as well as good rate capability and cycling stability compared with other samples. It delivered capacities of 220 and 213 mAh g−1 at a current density of 30 mA g−1 when tested at room temperature and 55 °C, respectively. It still had capacities of 184 and 197 mAh g−1 after 50 cycles, which was noticeably higher than the known theoretical capacity of pure Li4Ti5O12 (175 mAh g−1). The excellent electrochemical performance of the nitrogen‐treated nanoporous composites could be attributed to the improved morphology, dual phase crystal structure, and the presence of surface defects from nitrogen treatment.

Li4Ti5O12-rutile TiO2 nanosheet composite as a high performance anode material for lithium-ion battery

Li4Ti5O12 and Li4Ti5O12-rutile TiO2 nanosheet composite were synthesized by a facile solvothermal method with further calcination. The addition of rutile TiO2 does not affect the crystal structure, particle size, morphology of spinel Li4Ti5O12. XRD shows that the molar ratio of Li/Ti has much influence on the chemical composition of the products. TEM indicates that both Li4Ti5O12 and Li4Ti5O12-rutile TiO2 samples are composed of nanoplates with particle size of 50–100 nm. CV and EIS imply that Li4Ti5O12-rutile TiO2 has higher reversible intercalation and deintercalation of Li+, larger lithium-ion diffusion coefficient and smaller charge transfer resistance corresponding to a much higher conductivity than those of Li4Ti5O12 corresponding to the extraction of Li+ ions. Li4Ti5O12-rutile TiO2 material exhibits excellent cycling stability and rate capability in relevant lithium-ion batteries, which can retain a capacity of 120.5 mAh g−1 after 150 cycles at 5 C charge–discharge rate cycled between 1.0 and 2.5 V. This performance is much better than that of pristine Li4Ti5O12 (82.2 mAh g−1), whose capacity fades seriously. Li4Ti5O12-rutile TiO2 also exhibits a good rate performance in a broad voltage window. The capacities of Li4Ti5O12-rutile TiO2 and Li4Ti5O12 charge-discharged at 12 C rates remains at 125.4 and 50.2 mAh g−1 cycled between 0.0 and 2.5 V after 200 cycles, respectively. The enhanced performance of Li4Ti5O12-rutile TiO2 is ascribed to the improved electronic conduction and the reduced polarization resulting from the rutile TiO2 modification together with nanosized structure.

Nanotube-Constructed Li4Ti5O12-TiO2 Hybrid Spheres for Lithium Ion Batteries

Introduction Spinel Li4Ti5O12 and anatase TiO2 have been regarded as two typical alternative anode materials for rechargeable lithium-ion batteries (LIBs) to the commercial graphite because of their better safety and low volume expansion.1-3 The flat lithium insertion potential plateau of spinel Li4Ti5O12 locates at 1.55 V, which is above the solid electrolyte interface (SEI) and the lithium dendrite formation potentials, thus making it much safer. Also, the spinel Li4Ti5O12 is “zero strain” insertion, which endows the material a high potential of long cycle life. Similarly, anatase TiO2 features a potential plateau of ~1.7 V along with a low volume expansion of 3-4%. More importantly, the reduction of the particle size to nanoscale allows nearly 1 Li+ insertion into the anatase host structure, resulting in a high capacity of more than 300 mA h g- 1 theoretically. By combining the two materials, high safety and long cycle life as well as high capacity are expected. However, the instinct electronic conductivity for both materials is very low.4-7 Here, we report on the large-scale fabrication of nanotube-constructed Li4Ti5O12-TiO2 hybrid spheres (L-T-SPs), and the evaluation of their lithium storage properties. The hybrid exhibits a high capacity and long cycle life, benefitting from the tiny tubular morphology, defects in the grain boundary of the Li4Ti5O12-TiO2 hybrid and the synergistic effects of the two phases. Experimental Typically, the L-T-SPs product was prepared by a modified hydrothermal route, followed by an ion-exchange and post annealing processes. The microstructure of the L-T-SPs product were determined by scanning electron microscopy (SEM). The working electrodes were fabricated by mixing the L-T-SPs material, super P and polyvinylidene fluoride (PVDF) dissolved in N-methyl-2-pyrrolidone (8:1:1), and then coated onto a Cu foil. A lithium foil was used as the counter and reference electrode, Celgard 2300 as the separator, and 1 M LiPF6 in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (1:1) as the electrolyte. Galvanostatic charge-discharge measurements were performed on a Land Battery Measurement System (Land, China) at various current densities. Results and Discussion The synthesis process is schematically illustrated in Fig. 1a. The titanic acid (HTO) precursor was firstly treated by LiOH to exchange the H+ ions with Li+ ions, forming an intermediate containing Li, Ti and O elements (Li-Ti-O spheres). The Li4Ti5O12-TiO2 product was obtained by post annealing the intermediate. The SEM images in Fig. 1b and 1c shows the spherical morphology of the product. Each individual urchin-like microsphere consists of numerous tiny nanotubes. The lithium storage performance of the as-prepared L-T-SPs product was evaluated using lithium half-cells. Fig. 1d demonstrates the initial two cycles of the galvanostatic charge-discharge profiles. There are two distinct voltage plateaus located at ~1.7 and 1.55 V in the discharge process, assigned to the insertion of lithium into the anatase and the Li4Ti5O12 host structures, respectively. The cycle performances of the L-T-SPs electrode are presented in Fig. 1e. Capacities of ~140 mA h g- 1 at 5 C and ~110 mA h g- 1 at 20 C can be obtained. Moreover, the capacity at 20 C retained for 100 cycles without obvious decay, indicating excellent cyclability of the L-T-SPs electrode. The tiny tubular microstructure integrated with the defects in the grain boundary and the synergy between the spinel Li4Ti5O12 and anatase TiO2 contribute to the enhanced lithium storage performance of the L-T-SPs electrode. Figure captions: Figure 1. (a) Schematic illustration of the formation process for the L-T-SPs product, (b,c) SEM images of the L-T-SPs product, (d,e) The charge-discharge profiles of the L-T-SPs electrodes in the initial two cycles and their cycle performances at 5 and 20 C. References 1 M. Wagemaker, W. J. H. Borghols and F. M. Mulder, J . Am . Chem . Soc . 2007, 129, 4323-4327. 2 V. Gentili, S. Brutti, L. J. Hardwick, A. R. Armstrong, S. Panero and P. G. Bruce, Chem. Mater. 2012, 24, 4468-4476. 3 Y. Q. Wang, L. Gu, Y. G. Guo, H. Li, X. Q. He, S. Tsukimoto, Y. Ikuhara and L. J. Wan, J . Am . Chem . Soc . 2012, 134, 7874-7879. 4 C. J. Chen, X. L. Hu, P. Hu, Y. Qiao, L. Qie, Y. H. Huang, Eur. J. Inorg. Chem . 2013, 30, 5320. 5 A. G. Dylla, G. Henkelman, K. J. Stevenson, Acc. Chem. Res. 2013, 46, 1104. 6 C. J. Chen, X. L. Hu, Y. Jiang, Z. Yang, P. Hu, Y. H. Huang, Chem . Eur. J. 2014, 20, 1383. 7 E. Kang, Y. S. Jung, G. H. Kim, J. Chun, U. Wiesner, A. C. Dillon, J. K. Kim and J. Lee, Adv . Funct . Mater . 2011, 21, 4349-4357. Figure 1

Synthesis of porous sword-shaped Li4Ti5O12 anode material by a normal pressure hydrolysis and ion exchange method

Abstact A series of Li–Ti–O compounds (Li2TiO3, Li4Ti5O12, TiO2 and their composites) are synthesized by a normal pressure hydrolysis and an ion exchange method. XRD results indicate that the product gradually changes to Li4Ti5O12–Li2TiO3 composite, Li4Ti5O12, Li4Ti5O12–TiO2 composite and anatase TiO2 with increasing the exchange amount of Li+ and H+ of the precursors. SEM results reveal that the amount of Li-ions in the precursor greatly affects the morphology of the Li–Ti–O compounds. The Li4Ti5O12 shows a porous sword shape with several tens of microns in length, 2–4 μm in width and 0.5–1 μm in thickness. The porous swords are composed of the particles in the size of 0.5–0.8 μm; further, TEM results reveal that the particles are actually the aggregations of nanoscale crystalline grains (80–250 nm). The porous sword-shaped Li4Ti5O12 shows the specific charge capacities of 167.9, 162.2 and 103.1 mAh g−1 at 0.1 C, 1 C and 20 C rates, respectively, and exhibits excellent cycling performance.

Hydrothermal Synthesis of Li4Ti5O12/TiO2 Nano-composite As High Performance Anode Material for Li-Ion Batteries

A facile hydrothermal approach has been developed to synthesize the nanostructured dual phase Li4Ti5O12/TiO2 composite. The fabrication process simply involves the hydrothermal treatment of tetrabutyl titanate with LiOH in glycerol-water solution and a subsequent calcination procedure. The calcination treatment at 500°C leads to the phase evolution from Li1.81H0.19Ti2O5•nH2O to Li4Ti5O12/TiO2 composite with a particle size of about 30nm. It is found that glycerol as chelating agent plays an important role in the formation of TiO2. The Li4Ti5O12 and anatase TiO2 nano-composite exhibits rich hierarchical pores and a specific surface area of 91.88m2g−1, delivers ultrahigh rate performance of over 150mA h g−1 at 20C, as well as superior capacity retention of 151.4 mAh g−1 after 100 cycles at 1C. It is therefore concluded that Li4Ti5O12/TiO2 nano-composite is a promising candidate for applications in high rate lithium ion batteries.

Dual phase Li4Ti5O12–TiO2 nanowire arrays as integrated anodes for high-rate lithium-ion batteries

Lithium titanate (Li4Ti5O12) is well known as a zero strain material inherently, which provides excellent long cycle stability as a negative electrode for lithium ion batteries. However, the low specific capacity (175mAhg−1) limits it to power batteries although the low electrical conductivity is another intrinsic issue need to be solved. In this work, we developed a facile hydrothermal and ion-exchange route to synthesize the self-supported dual-phase Li4Ti5O12–TiO2 nanowire arrays to further improve its capacity as well as rate capability. The ratio of Li4Ti5O12 to TiO2 in the dual phase Li4Ti5O12–TiO2 nanowire is around 2:1. The introduction of TiO2 into Li4Ti5O12 increases the specific capacity. More importantly, by interface design, it creates a dual-phase nanostructure with high grain boundary density that facilitates both electron and Li ion transport. Compared with phase-pure nanowire Li4Ti5O12 and TiO2 nanaowire arrays, the dual-phase nanowire electrode yielded superior rate capability (135.5 at 5C, 129.4 at 10C, 120.2 at 20C and 115.5mAhg−1 at 30C). In-situ transmission electron microscope clearly shows the near zero deformation of the dual phase structure, which explains its excellent cycle stability.

Design and synthesis of dual-phase Li4Ti5O12–TiO2 nanoparticles as anode material for lithium ion batteries

Dual-phase Li4Ti5O12–TiO2 nanocrystallines were prepared by a solvothermal process. The product exhibited initial discharge capacities of 315 and 230mAh/g at the discharge rates of 0.1 and 1C, respectively. After 80 cycles, the Li4Ti5O12–TiO2 nanocrystallines retained 83% and 87% of its initial discharge capacities at the 0.1 and 1C rates, respectively. The high electrochemical performance indicates that dual-phase Li4Ti5O12–TiO2 nanocrystallines are highly promising anode materials for lithium ion battery applications.

Synthesis of high performance Li4Ti5O12 microspheres and TiO2 nanowires from natural ilmenite

In this work, natural ilmenite is transformed into either Li4Ti5O12 microspheres or TiO2 nanowires through a series of chemical and thermal processes by the combination of metallurgy and materials science. Both of the synthesized materials demonstrate excellent electrochemical performance.

Petal-like Li4Ti5O12–TiO2 nanosheets as high-performance anode materials for Li-ion batteries

A petal-like nanostructured Li4Ti5O12-TiO2 composite has been synthesized by a novel, simple, ultrafast, low-cost, and environmentally benign process and investigated as an anode material for Li-ion batteries. This work introduces a special solution system not slurry to synthesize a spherical flower-like Li4Ti5O12-TiO2 composite by boiling followed by solid-state calcination at a low temperature of 500 °C for 3 h. Well-crystallized Li4Ti5O12-TiO2 with relatively larger amounts (18.80 weight%) of anatase TiO2 can be obtained, which is different from conventional carbon coating, metal doping and trace TiO2 coating. Owing to the relatively low calcined temperature, the flower-like shape of the precursor powder is maintained after post-treatment. Because of the rough and porous nanostructured particles and mutually complementary intrinsic advantages between Li4Ti5O12 and TiO2, the Li4Ti5O12-TiO2 composite obtained at a relatively low calcined temperature shows excellent electrochemical performance. There are two pairs of long and flat voltage plateaus during charge and discharge at 0.1 C rate, which are not shown in other Li4Ti5O12-TiO2 composites. The initial discharge capacities are 185.5, 177.2, 167.3, 145.8, 137.7, 127.5 and 112.5 mA h g(-1) at the 0.1, 0.5, 1, 2, 5, 10 and 20 C rates, respectively. After 100 cycles, the prepared Li4Ti5O12 retains 99.6%, 98.0%, 98.2% and 97.1% of its initial discharge capacities at the 2, 5, 10 and 20 C rates, respectively. After total 450 cycles at 1, 2, 5, 10 and 20 C rates, the cell returns to C/10 and still exhibits a remarkably high discharge capacity of 175.8 mA h g(-1) which is 94.8% of the initial discharge capacity at 0.1 C rate.

Synthesis and electrochemical performance of high-rate dual-phase Li4Ti5O12–TiO2 nanocrystallines for Li-ion batteries

Dual-phase Li4Ti5O12–TiO2 nanocrystallines are prepared by a hydrothermal process and subsequent heat treatment. The as-prepared Li4Ti5O12–TiO2 nanocrystallines measure around 15–25nm in size and have abundant phase interfaces. Electrochemical measurements demonstrate that dual-phase Li4Ti5O12–TiO2 exhibit good electrochemical performance over individual single-phase Li4Ti5O12, especially at high current rates. Initial discharge capacities of dual-phase Li4Ti5O12–TiO2 nanocrystallines are 241 and 202mAhg−1 at discharge rates of 0.2 and 5C, respectively. Even after 50 cycles at 20C, the capacity still remains 140mAhg−1, which is four times greater than that of single-phase Li4Ti5O12 (29mAhg−1). The high electrochemical performance indicates that dual-phase Li4Ti5O12–TiO2 nanocrystallines are highly promising anode materials for lithium ion battery applications.

Li4Ti5O12–TiO2 composite anode material for lithium-ion batteries

In an effort to improve the rate-capability of Li4Ti5O12 anode material, a dual-phase composite Li4Ti5O12–TiO2 is in situ prepared via a solvothermal route. The Li4Ti5O12–TiO2 composite shows higher reversible capacity and better rate-capability compared to single phase Li4Ti5O12. The TiO2 can decrease significantly the particle size of Li4Ti5O12–TiO2 powders due to a steric hindrance effect, which thereby shortens the lithium ion diffusion distance and enhances the electrode reaction. Meanwhile, anatase TiO2 can contribute some capacity to the Li4Ti5O12–TiO2 electrode. Coating the Li4Ti5O12–TiO2 composite with carbon (∼2.5 wt.%) can further improve the rate-capability of Li4Ti5O12–TiO2 electrode, a reversible capacity of ∼140 mA h g−1 is maintained after 100 cycles at 5 C.