Effects of carbon sources on electrochemical performance of Li_4Ti_5O_(12)/C composite anode materials

Li4Ti5O12/C composite materials were synthesized by two-step solid state reaction method with glucose, sucrose, and starch as carbon sources, respectively. The effects of carbon sources on the structure, morphology, and electrochemical performance of Li4Ti5O12/C composite materials were investigated by SEM, XRD and electrochemical tests. The results indicate that carbon sources have almost no effect on the structure of Li4Ti5O12/C composite materials. The initial discharge capacities of the Li4Ti1O12/C composite materials are slightly lower than those of as-synthesized Li4Ti5O12. However, Li4Ti5O12/C composite materials show better electrochemical rate performance than the as-synthesized Li4Ti5O12. The capacity retention （79%） of the Li4Ti5O12/C composite materials with starch as carbon source, is higher than that of Li4Ti5O12/C composite materials with glucose and sucrose as carbon source at current rate of 2.0C.

Preparation and characterization of spinel Li_4Ti_5O_(12) anode materialfrom industrial titanyl sulfate solution

Metatitanic acid was synthesized from industrial titanyl sulfate solution via controlling pH during hydrolyzing process. Inductively coupled plasma(ICP)analysis confirmed that a little Fe,Mg and Ca were deposited into precursor TiO2·H2O.Spinel Li4Ti5O12 was prepared by sintering amorphous mixture at 800℃for 16 h.The amorphous mixture was activated by ball-milling at room temperature,using the as-prepared TiO2·H2O and Li2CO3 as raw materials.The sample was characterized by X-ray diffractometry,scanning electron microscopy and electrochemical charge and discharge test.The results show that spinel Li4Ti5O12 is obtained,but it contains a few rutile TiO2 impurities.The sample has fine particles with size of around 50 nm and homogenous size distribution.At room temperature,the initial reversible specific capacity of the sample is 136.9,128.0,119.2 and 96.3 mA·h/g at 0.1C, 1C,2C and 5C,respectively,and the sample shows excellent cycling performance.

Kinetics of synthesis of Li_4Ti_5O_(12) through solid-solid reaction

Sohd-solid reaction under low heat or low temperature is an approach to synthesize various kinds of materials that were widely used in electrochemistry field. In this paper a theoretical treatment has been presented for analyzing the mechanism of sohd-solid reaction and deriving a series of formulae to describe the variation and rate of reactions. This new model has been used in the manufacturing of spinel Li4Ti5O12. The results show that this new model works very well and will play a useful role for guiding the manufacturing of electrochemical materials.

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.

Single Phase Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB>Synthesis for Nanoparticles by Two Steps Sintering

Li4Ti5O12 has been noticed about a negative electrode of a high powered and safe lithium ion secondary battery. These properties require single phase, high crystallization, larger specific surface area and fine nanoparticles. This study carried out the noble synthesis of Li4Ti5O12 using a solid phase synthesis by two steps sintering. These results showed Li4Ti5O12 of 6.1 m2&middotg-1?and diameter of 110 nm with the single phase and high crystallization. Li2TiO3 will play an important role in this reaction, obtained by pre-sintering as a precursor.

Ab initio studies on n-type and p-type Li_4Ti_5O_(12)

This paper studies the structure and electronic properties of Li4Ti5O12, as anode material for lithium ion batteries, from first principles calculations. The results suggest that there are two kinds of unit cell of Li4Ti5O12： n-type and p-type. The two unit cells have different structures and electronic properties： the n-type with two 16d site Li ions is metallic by electron, while the p-type with three 16d Li ions is metallic by hole. However, the Li4Ti5O12 is an insulator. It is very interesting that one n-type cell and two p-type cells constitute one Li4Ti5O12 supercell which is insulating. The results show that the intercalation potential obtained with a p-type unit cell with one additional electron is quite close to the experimental value of 1.5 V.

Electrochemical Performance of Li_4Ti_5O_(12) Prepared by Different Methods

A series of Li4Ti5O12 materials were prepared by three different methods： solvothermal, sol-gel, and solid-state reaction methods. Phase composition, morphology, and particle sizes of the samples were studied by powder X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Electrochemical properties of the samples were investigated by charge-discharge tests. It is demonstrated that both sol-gel and solid-state reaction methods provided good control over the chemical composition and microstructure of the active material, in which sol-gel method yielded a fine Li4Ti5O12 spinel having an initial specific capacity of 146 mAh g-1 and low capacity fade during cycling. Comparatively, the solid-state method is simple and promising to prepare Li4Ti5O12 for commercial applications.

Low-temperature Synthesis of Peony-like Spinel Li4Ti5O12 as a High-performance Anode Material for Lithium Ion Batteries

Peony-like spinel Li4Ti5O12 was synthesized via calcination of precursor at the temperature of 400 ℃, and the precursor was prepared through a hydrothermal process in which the reaction of hydrous titanium oxide with lith- ium hydroxide was conducted at 180 ℃. The as-prepared product was investigated by SEM, TEM and XRD, re- spectively. As anode material for lithium ion battery, the Li4Ti5O12 obtained was also characterized by galvanostatic tests and cyclic voltammetry measurements. It is found that the peony-like Li4Ti5O12 exhibited high rate capability of 119.7 mAh·g ^-1 at 10 C and good capacity retention of 113.8 mAh·g ^-1 after 100 cycles at 5 C, and these results indicate the peony-like Li4Ti5O12 has promising applications for lithium ion batteries with high performance.

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.

Ultralong-life and high-rate web-like Li4Ti5O12 anode for high-performance flexible lithium-ion batteries

Flexible lithium ion batteries （LIBs） have recently attracted increasing attention as they show unique promising advantages, such as flexibility, shape diversity, and light weight. Similar to conventional LIBs, flexible LIBs with long cycle life and high-rate performance are very important for applications of high performance flexible electronics. Herein, we report a three-dimensional （3D） web-like binderfree Li4Ti5O12 （LTO） anode assembled from numerous 1D nanowires exhibiting excellent cycling performance with high capacities of 153 and 115 mA·h·g^-1 after 5,000 cycles at 2 C and 20 C, respectively, and excellent rate property with a capacity of 103 mA·h·g^-1 even at a very high current rate of 80 C. Surprisingly, a flexible full battery assembled from the web-like LTO nanostructure and LiMn2O4 （LMO） nanorods exhibited a high capacity of 125 mA·h·g^-1 at high current rate of 20 C, and showed excellent flexibility with little performance degradation even in seriously bent states.

Synthesis and characterization of Li_4Ti_5O_(12) via a hydrolysis process from TiCl_4 aqueous solution

Spinel-type lithium and titanium composite oxide Li4TisO12 was successfully synthesized via a novel hydrolysis method followed by calcination using titanium tetrachloride （TIC14） and lithium hydroxide （LiOH.H2O） as raw materials. Three major factors, including LiOH con- centration, LiOH dosage, and hydrolysis temperature were studied for optimizing the synthetic conditions to obtain a phase-pure Li4Ti5012. The physical and electrochemical properties of samples were characterized by X-ray dif- fraction （XRD）, thermogravimetric analysis （TGA）, fourier transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, and constant current discharge-charge test. The FT-IR results indicate the presence of [TiO6] octahedra. The SEM images show that the Li4Ti5O12 pre- cursor obtained is an amorphous solid with an irregular and rough morphology. It is revealed that the phase-pure spinel Li4Ti5O12 powders with well crystallization and regular morphology can be obtained by calcining the precursor at 800 ℃ for 6 h. The constant current discharge-charge tests indicate that the Li4TisO12 material delivers an excellent cycling ability, maintaining 93.8 % of its initial specific capacity after 60 cycles at a current density of 0.5C.

Effect of Calcining Temperature on the Structure of Li_4Ti_5O_(12)

1 Introduction Recently there had considerable interest in Li4Ti5O12 as a potential anode for use in Li-ion batteries. Usually, it was used as an anode combined with a high voltage cathode[1-5]. It has many advantages compared to the currently used graphite. For example, it presents virtually unlimited cycle life due to zero strain or volume change when lithium intercalates into and de-intercalates from[6]. Generally, Li4Ti5O12 was prepared by a solid-state reaction from stoichiometric amounts of Li2CO3...