Dual-phase Li4Ti5O12 TiO2 Research Articles

Facile synthesis of dual-phase lithium titanate nanowires as anode materials for lithium-ion battery

A facile method to synthesize dual phase Li4Ti5O12-TiO2 nanowires and their performance as anode material for lithium-ion battery are investigated. Li4Ti5O12-TiO2 nanowires are obtained from titanium nanoparticles by applying the wet corrosion process for the nanostructure formation and subsequent ion exchange processes. Post-heat treatments are adopted to tune the mixed phase composition of the nanowires, which significantly influences the electrochemical performance. The dual phase nanowires-based anode materials with a TiO2: Li4Ti5O12 phase ratio of 7:3 exhibit the highest delithiation capacity of 180 mAh/g and 105 mAh/g at 0.5 C and 5 C, respectively. In addition, it shows a remarkable capacity retention of ~95% after 150 cycles at 5 C, which is a significant improvement compared to previous reports on Li4Ti5O12-TiO2 based anode materials synthesized at low temperatures. This dual phase anode material based on Li4Ti5O12-TiO2 nanowires combines two advantages: i) High aspect ratio nanostructures increase the surface area and shorten the diffusion path of lithium ions and ii) the dual phase accelerates ion/electron migration owing to abundant interfaces/grain boundaries. Consequently, the proposed synthesis route for Li4Ti5O12-TiO2 nanowires provides an effective and highly reproducible approach to fabricate dual phase Li4Ti5O12-TiO2 nanowires as anode materials for lithium ion batteries.

Role of TiO2 Phase Composition Tuned by LiOH on The Electrochemical Performance of Dual-Phase Li4Ti5O12-TiO2 Microrod as an Anode for Lithium-Ion Battery

In this study, a dual-phase Li4Ti5O12-TiO2 microrod was successfully prepared using a modified hydrothermal method and calcination process. The stoichiometry of LiOH as precursor was varied at mol ratio of 0.9, 1.1, and 1.3, to obtain the appropriate phase composition between TiO2 and Li4Ti5O12. Results show that TiO2 content has an important role in increasing the specific capacity of electrodes. The refinement of X-ray diffraction patterns by Rietveld analysis confirm that increasing the LiOH stoichiometry suppresses the TiO2 phase. In the scanning electron microscopy images, the microrod morphology was formed after calcination with diameter sizes ranging from 142.34 to 260.62 nm and microrod lengths ranging from 5.03–7.37 μm. The 0.9 LiOH sample shows a prominent electrochemical performance with the largest specific capacity of 162.72 mAh/g and 98.75% retention capacity achieved at a rate capability test of 1 C. This finding can be attributed to the appropriate amount of TiO2 that induced the smaller crystallite size, and lower charge transfer resistance, enhancing the lithium-ion insertion/extraction process and faster diffusion kinetics.

Synthesis of dual-phase Li4Ti5O12-TiO2 nanowires as anode for lithium-ion battery

Dual-phase Li4Ti5O12-TiO2 was successfully synthesized by a hydrothermal method at various temperatures of 180, 200 and 220 °C for 24 h. SEM images show that the morphology of dual-phase Li4Ti5O12-TiO2 is nanowire with sizes in the range of 4–6 μm in length and 19–97 nm in diameter. The as-prepared dual-phase Li4Ti5O12-TiO2 with the hydrothermal temperature of 200 °C exhibits excellent cycling performance and high rate capability when used as anode for lithium-ion batteries, obtaining reversible discharge capacity of 93.22 mAh/g at 0.1C and capacity fading less than 5%. It is attributed to the most crystalline phase of Li4Ti5O12 (LTO) 200 °C, the most stable polarization curve and the unique structure of nanowires providing a large surface area which maintains good electronic contact between particles. This result demonstrates that dual-phase Li4Ti5O12-TiO2 has a high potential as anode material for high-rate application of lithium-ion battery.

Combined Modification of Dual-Phase Li4Ti5O12-TiO2 by Lithium Zirconates to Optimize Rate Capabilities and Cyclability.

The low electrical conductivity and ordinary lithium-ion transfer capability of Li4Ti5O12 restrict its application to some degree. In this work, dual-phase Li4Ti5O12-TiO2 (LTOT) was modified by composite zirconates of Li2ZrO3, Li6Zr2O7 (LZO) to boost the rate capabilities and cyclability. When the homogeneous mixture of LiNO3, Zr(NO3)4·5H2O and LTOT was roasted at 700 °C for 5 h, the obtained composite achieved a superior reversible capacity of 183.2 mAh g-1 to the pure Li4Ti5O12 after cycling at 100 mA g-1 for 100 times due to the existence of a scrap of TiO2. Meanwhile, when the composite was cycled by consecutively doubling the current density between 100 and 1600 mA g-1, the corresponding reversible capacities are 183.2, 179.1, 176.5, 173.3, and 169.3 mAh g-1, signifying the prominent rate capabilities. Even undergoing 1400 charge/discharge cycles at 500 mA g-1, a reversible capacity of 144.7 mAh g-1 was still attained, denoting splendid cyclability. From a series of comparative experiments and systematic characterizations, the formation of LZO meliorated both the Li+ migration kinetics and electrical conductivity on account of the concomitant superficial Zr4+ doping, responsible for the comprehensive elevation of the electrochemical performance.

Dual phase Li4Ti5O12-TiO2 hierarchical hollow microspheres as anode materials for high rate lithium-ion batteries

Dual phase Li4Ti5O12-TiO2 hierarchical hollow microspheres composed of nanosheets are successfully fabricated by the calcination of hydrothermal product obtained from lithium peroxotitanate complex solution. Low-cost industrial H2TiO3 particles are chosen as titanium sources, which is significant for the inexpensive and large-scale production of Li4Ti5O12-TiO2 composite material. The Li4Ti5O12-TiO2 electrode yields excellent rate capability (151, 139 and 134 mA h g-1 at 10, 20 and 25 C, respectively) and good cycling stability (96% capacity retention after 500 cycles at 10 C). The mesoporous hierarchical morphology and high grain boundary density are likely the contributing factors to the excellent electrochemical performance of Li4Ti5O12-TiO2 composite.

Electrospun dual phase Li4Ti5O12-TiO2/C nanocomposites as anodes for high-rate lithium-ion batteries

ABSTRACTDual phase Li4Ti5O12-TiO2/C nanocomposites have been one-step synthesized by the method of electrospinning. When the Li4Ti5O12-TiO2/C nanocomposites are used as anode material for lithium-ion batteries, it exhibits excellent capacity of 186.5 mAh/g at 4000 mA/g with a good cycling performance. Simultaneously, it owns remarkable rate capability and reversible capability. The introduction of TiO2 enhances both the electric conductivity and the lithium ion diffusivity in Li4Ti5O12. And then it has good electrochemical performance.

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 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.

Amorphous Carbon Coated Dual Phase Li4Ti5O12-TiO2 Nanocomposite as Anode Material for Li-Ion Battery

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